Semiconductor device

ABSTRACT

Provided is a semiconductor device comprising a first interlayer insulating film formed over a semiconductor substrate and having a wiring trench; a wiring portion which has a first barrier metal layer formed over the side walls and bottom surface of said wiring trench, a first conductor layer formed over said first barrier metal layer so as to embed said wiring trench with said first conductor layer, and a capping barrier metal film formed over the surface of said first conductor layer; a second interlayer insulating film formed over said first interlayer insulating film and having a connecting hole; and a connecting portion which has a second barrier metal layer formed over the side walls and bottom surface of said connecting hole, and a second conductor layer formed over said second barrier metal layer so as to embed said connecting hole with said second conductor layer; wherein at a joint between said connecting portion and said wiring portion, at least either one of said second barrier metal layer or said capping barrier metal film on the bottom surface of said connecting hole is removed. According to the present invention, contact resistance between the first-level interconnect and plug can be reduced and electromigration resistance can be improved.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a semiconductor integrated circuit device, particularly to a technique effective when adapted to a connecting portion between interconnects.

[0002] In recent years, since the interconnects of semiconductor integrated circuit devices (semiconductor devices) tend to be miniaturized and multilayered, studies have been made on the so-called damascene technique for forming a trench in an insulating film, and embedding it with a conductive film, thereby forming an interconnect.

[0003] This damascene technique can be roughly divided into single damascene technique and dual damascene technique. In the former one, a wiring trench and a trench for connecting interconnects are embedded by different steps, while in the latter one, a wiring trench and a connecting trench are embedded simultaneously.

[0004] As a conductive film to be filled in such a trench, a copper film or the like is employed.

[0005] Inside of this trench, a conductive film having barrier properties is formed in order (1) to prevent diffusion, in an insulating film, of a metal constituting the conductive film to be embedded (the metal is copper when the conductive film is a copper film), or (2) when an insulating film is composed of an oxide such as silicon oxide film, to prevent oxidation of the conductive film which will otherwise occur owing to the contact between the silicon oxide film and the conductive film.

[0006] Over the conductive film (for example, copper film) to be embedded in the trench, an insulating film having barrier properties such as silicon nitride film is formed to prevent diffusion of the metal into the insulating film to be formed over the conductive film or to prevent oxidation thereof by the insulating film.

SUMMARY OF THE INVENTION

[0007] The silicon nitride film however has a high dielectric constant so that an RC time constant of the interconnect becomes large, thereby disturbing the high-speed operation of the device.

[0008] Diffusion (transfer) of the metal constituting the conductive film causes electromigration. As a result of an investigation on the diffusibility of copper, activation energy of diffusion is presumed to be greater (copper diffuses with more difficulty) on a copper—barrier film interface than that on a copper—silicon nitride film interface. Accordingly, the electromigration lifetime is limited by the activation energy of the copper diffusion on a copper—silicon nitride film interface.

[0009] If on the bottom surface of a connecting portion between interconnects, voids are caused by electromigration, a contact area between the connecting portion and the underlying interconnect becomes small, leading to accelerated lowering in an interconnect lifetime.

[0010] The present inventors have investigated the formation, over the interconnect, of a conductive film such as tungsten (W) film having barrier properties.

[0011] For example, a technique of forming a cap (WCAP) composed of W over an interconnect made of an Al—Cu alloy (AlnCuy ALLOY) is disclosed in U.S. Pat. No. 6,147,402.

[0012] In U.S. Pat. No. 6,114,243, disclosed is a technique of forming, in a so-called damascene structure, a conductive capping layer (26) over a copper layer (24), forming thereover a via or dual damascene opening (35), and then forming a barrier layer (36) and a copper layer (38). The numerals in parentheses are those described in the patent gazette.

[0013] Formation of a conductive film (which will hereinafter be called “capping barrier metal layer”), such as tungsten (W) film, having barrier properties over the interconnect however leads to a structure in which a metal film constituting the interconnect, a capping barrier metal layer, a barrier metal layer and a metal layer constituting a connecting portion have been stacked in this order between the interconnect and the connecting portion. Contact resistance between these films inevitably increases in such a structure.

[0014] When transfer of metal atoms due to electromigration occurs in such a structure, existence of the capping barrier metal layer and barrier metal layer between the connecting portion and the interconnect disturbs transfer of the metal between the connecting portion and the interconnect.

[0015] As a result, generation frequency of voids increases and a potential causing disconnection heightens. As well as disconnection due to electromigration, similar disconnection presumably occurs owing to stress-induced peeling between a barrier metal and copper on the interface or stress-induced void formation, that is, stress migration.

[0016] An object of the present invention is to reduce contact resistance between the interconnect and connecting portion.

[0017] Another object of the present invention is to improve reliability, more specifically, to reduce a generation frequency of voids or disconnection due to electromigration or to reduce a generation frequency of disconnection due to stress migration.

[0018] A further object of the present invention is to improve the characteristics of a semiconductor device.

[0019] The above-described objects and novel features of the present invention will be apparent by the description herein and accompanying drawings.

[0020] The typical inventions, among the inventions disclosed by the present application, will next be outlined briefly.

[0021] (1) A semiconductor device according to the present invention comprises:

[0022] a first interlayer insulating film formed over a semiconductor substrate and having a wiring trench;

[0023] a wiring portion which has a first barrier metal layer formed over the side walls and bottom surface of the wiring trench, a first conductor layer formed over the first barrier metal layer so as to embed the wiring trench with the first conductor layer, and a capping barrier metal film formed over the surface of the first conductor layer;

[0024] a second interlayer insulating film formed over the first interlayer insulating film and having a connecting hole; and

[0025] a connecting portion which has a second barrier metal layer formed over the side walls and bottom surface of the connecting hole, and a second conductor layer formed over the second barrier metal layer so as to embed the connecting hole with the second conductor layer;

[0026] wherein at a joint between the connecting portion and the wiring portion, at least either one of the second barrier metal layer or the capping barrier metal film on the bottom surface of the connecting hole is removed.

[0027] (2-1) A manufacturing method of a semiconductor device according to the present invention comprises:

[0028] forming a first interlayer insulating film over a semiconductor substrate,

[0029] forming a wiring trench in the first interlayer insulating film,

[0030] forming a first barrier metal layer over the side walls and bottom surface of the wiring trench,

[0031] forming a first conductor layer over the first barrier metal layer so as to embed the wiring trench with the first conductor layer,

[0032] forming a capping barrier metal film over the surface of the first conductor layer,

[0033] forming a second interlayer insulating film over the first interlayer insulating film,

[0034] forming a connecting hole in the second interlayer insulating film,

[0035] forming a second barrier metal layer over the side walls and bottom surface of the connecting hole, and

[0036] forming a second conductor layer over the second barrier metal layer so as to embed the connecting hole with the second conductor layer;

[0037] wherein the capping barrier metal film is removed only from the overlapping portion of the connecting hole with the wiring trench in the step of forming the connecting hole.

[0038] (2-2) The manufacturing method of a semiconductor device as described above in (2-1), wherein at the overlapping portion of the wiring trench and the connecting hole, the wiring trench is formed greater in area than the connecting hole.

[0039] (2-3) The manufacturing method of a semiconductor device as described above in (2-1), which further comprises, prior to the formation of the second conductor layer, removing the second barrier metal layer from the bottom surface of the connecting hole.

[0040] (2-4) The manufacturing method of a semiconductor device as described above in (2-1), wherein the barrier metal layer is formed from a single layer film of any one of Ta, TaN, TaSiN, W, WN, WSiN, Ti, TiN and TiSiN; or a laminate film obtained by stacking a plurality of any two or greater of Ta, TaN, TaSiN, W, WN, WSiN, Ti, TiN and TiSiN.

[0041] (2-5) The manufacturing method of a semiconductor device as described above in (2-1), wherein the capping barrier metal film is formed from a metal layer composed mainly of W, WN, WsiN and W, a metal layer composed mainly of CoWP, CoWB or Co, a single layer film of any one of TiN, TiSiN, Ta, TaN and TaSiN, or a laminate film obtained by stacking any two of the metal layers and single layer films.

[0042] (2-6) The manufacturing method of a semiconductor device as described above in (2-1), wherein the conductor layer is formed from any one of Cu, a metal layer composed mainly of Cu, Al, a metal layer composed mainly of Al, Ag and a metal layer composed mainly of Ag.

[0043] (3) A semiconductor device according to the present invention comprises a first wiring structure and a second wiring structure, the first wiring structure having a first wiring portion and a first connecting portion formed thereover;

[0044] the first wiring portion having a first conductor layer, a first barrier metal layer formed over the side walls and bottom surface of the first conductor layer so as to surround the first conductor layer, and a first capping barrier metal film formed over the surface of the first conductor layer; and

[0045] the first connecting portion being formed over the first wiring portion and having a second conductor layer, and a second barrier metal layer formed over the side surfaces and the bottom surface of the second conductor layer so as to surround the second conductor layer; and

[0046] the second wiring structure being formed over the first wiring structure and having a second wiring portion and a second connecting portion formed thereover;

[0047] the second wiring portion having a third conductor layer, a third barrier metal layer formed over the side walls and bottom surface of the third conductor layer so as to surround the third conductor layer, and a second capping barrier metal film formed over the surface of the third conductor layer; and

[0048] the second connecting portion being formed over the second wiring portion and having a fourth conductor layer and a fourth barrier metal layer formed over the side surfaces and the bottom surface of the fourth conductor layer so as to surround the fourth conductor layer; wherein:

[0049] the first and second barrier metal layers and the first capping barrier metal film are different in structure from the third and fourth barrier metal layers and the second capping barrier metal film, respectively.

[0050] (4) A semiconductor device according to the present invention comprises:

[0051] a first insulating film formed over a semiconductor substrate;

[0052] a second insulating film formed over the first insulating film;

[0053] a wiring trench formed by selectively removing the first insulating film and the second insulating film;

[0054] a wiring portion having a first barrier metal layer formed over the side walls and bottom surface of the wiring trench, a first conductor layer formed over the first barrier metal layer so as to embed the wiring trench, and a capping barrier metal film formed over the surface of the first conductor layer;

[0055] a third insulating film formed over the second insulating film and having a connecting hole; and

[0056] a connecting portion having a second barrier metal layer formed over at least the side walls, of the side walls and the bottom surface, of the connecting hole, and a second conductor layer formed over the second barrier metal layer so as to embed the connecting hole;

[0057] wherein the second insulating film has a function as a barrier insulating film.

[0058] (5-1) A manufacturing method of a semiconductor device according to the present invention comprises:

[0059] forming a first insulating film over a semiconductor substrate,

[0060] forming a second insulating film over the first insulating film,

[0061] forming a wiring trench by selectively removing the first insulating film and the second insulating film,

[0062] forming a first barrier metal layer over the side walls and bottom surface of the wiring trench,

[0063] forming a first conductor layer over the first barrier metal layer so as to embed it in the wiring trench,

[0064] forming a capping barrier metal film over the surface of the first conductor layer,

[0065] forming a third insulating film over the second insulating film,

[0066] forming a connecting hole in the third insulating film,

[0067] forming a second barrier metal layer over at least the side walls, of the side walls and bottom surface, of the connecting hole, and

[0068] forming a second conductor layer over the second barrier metal layer so as to embed it in the connecting hole;

[0069] wherein the second insulating film functions as a barrier insulating film.

[0070] (5-2) The manufacturing method of a semiconductor device as described above in (5-1), further comprising forming a fourth insulating film having a function as a barrier insulating film over the capping barrier metal film.

[0071] (5-3) The manufacturing method of a semiconductor device as described above in (5-1), wherein the second insulating film is a low dielectric constant film formed from a material having a dielectric constant lower than that of a silicon nitride film or having a dielectric constant not greater than 5.5.

[0072] (5-4) The manufacturing method of a semiconductor device as described above in (5-3), wherein the low dielectric constant film is a film formed by CVD by using Si and C, Si and N, Si, C and N, Si, O and N, Si, O and C, Si, O, C and N, or TMS and N₂O.

[0073] (5-5) The manufacturing method of a semiconductor device as descried above in (5-1), wherein the second insulating film has a function as an etching stopper layer upon formation of the connecting hole.

[0074] (5-6) The manufacturing method of a semiconductor device as descried above in (5-2), wherein the fourth insulating film has a function as an etching stopper layer upon formation of the connecting hole.

[0075] (5-7) The manufacturing method of a semiconductor device as descried above in (5-1), which further comprises, prior to the formation of the second conductor layer, removing the second barrier metal layer from the bottom surface of the connecting hole.

[0076] (5-8) The manufacturing method of a semiconductor device as descried above in (5-1), which further comprises:

[0077] in the connecting hole forming step, removing the capping barrier metal film only from an overlapping portion of the connecting hole and wiring trench; and

[0078] prior to the second conductor layer forming step, removing the second barrier metal layer from the bottom surface of the connecting hole.

[0079] (5-9) The manufacturing method of a semiconductor device as described above in any one of (5-1) to (5-8), wherein:

[0080] the first and third insulating films include a low-dielectric constant film formed from a material having a dielectric constant lower than that of a silicon oxide film or having a dielectric constant of 3.7 or less.

[0081] (5-10) The manufacturing method of a semiconductor device as described above in (5-9), wherein:

[0082] the low dielectric constant film has Si an C, Si, C and O, Si, O and F, C and H, or Si, O, C and H; or in addition, is porous.

[0083] (6-1) A manufacturing method of a semiconductor device, which comprises:

[0084] (a) forming a first conductor layer in a first insulating film over a semiconductor substrate,

[0085] (b) forming a capping barrier metal film over the surface of the first conductor layer,

[0086] (c) forming a second insulating film over the capping barrier metal film and first insulating film and then, forming a third insulating film over the second insulating film,

[0087] (d) selectively removing the second and third insulating films to form a connecting hole which exists both in the second insulating film and third insulating film and extends from the bottom of the wiring trench toward the capping barrier metal film,

[0088] (e) forming a barrier metal film over the side walls and bottom of the wiring trench and the side walls and bottom of the connecting hole,

[0089] (f) removing the barrier metal film from the bottom of the connecting hole, and

[0090] (g) forming a second conductor layer in the wiring trench and connecting hole.

[0091] (6-2) The manufacturing method of a semiconductor device as described above in (6-1), wherein in the barrier metal formation step, the barrier metal film is formed to be thicker at the bottom of the wiring trench than at the bottom of the connecting hole.

[0092] (6-3) The manufacturing method of a semiconductor device as described above in (6-2), wherein anisotropic etching is employed for the removal of the barrier metal film from the bottom of the connecting hole in the step (f).

[0093] (6-4) The manufacturing method of a semiconductor device as described above in (6-1), which further comprises, between the steps (d) and (e), removing the capping barrier metal film exposed from the bottom of the connecting hole.

BRIEF DESCRIPTION OF THE DRAWINGS

[0094]FIG. 1 is a fragmentary cross-sectional view of a substrate illustrating the manufacturing method of a semiconductor device according to Embodiment 1 of the present invention;

[0095]FIG. 2 is a fragmentary cross-sectional view of a substrate illustrating the manufacturing method of the semiconductor device according to Embodiment 1 of the present invention;

[0096]FIG. 3 is a fragmentary cross-sectional view of a substrate illustrating the manufacturing method of the semiconductor device according to Embodiment 1 of the present invention;

[0097]FIG. 4 is a fragmentary cross-sectional view of a substrate illustrating the manufacturing method of the semiconductor device according to Embodiment 1 of the present invention;

[0098]FIG. 5 is a fragmentary cross-sectional view of a substrate illustrating the manufacturing method of the semiconductor device according to Embodiment 1 of the present invention;

[0099]FIG. 6 is a fragmentary cross-sectional view of a substrate illustrating the manufacturing method of the semiconductor device according to Embodiment 1 of the present invention;

[0100]FIG. 7 is a fragmentary cross-sectional view of a substrate illustrating the manufacturing method of the semiconductor device according to Embodiment 1 of the present invention;

[0101]FIG. 8 is a fragmentary cross-sectional view of a substrate illustrating the manufacturing method of the semiconductor device according to Embodiment 1 of the present invention;

[0102]FIG. 9 is a fragmentary cross-sectional view of a substrate illustrating the manufacturing method of the semiconductor device according to Embodiment 1 of the present invention;

[0103]FIG. 10 is a fragmentary cross-sectional view of a substrate illustrating the manufacturing method of the semiconductor device according to Embodiment 1 of the present invention;

[0104]FIG. 11 is a fragmentary cross-sectional view of a substrate illustrating the manufacturing method of the semiconductor device according to Embodiment 1 of the present invention;

[0105]FIG. 12 is a fragmentary cross-sectional view of a substrate illustrating the manufacturing method of the semiconductor device according to Embodiment 1 of the present invention;

[0106]FIG. 13 is a fragmentary cross-sectional view of a substrate illustrating the manufacturing method of the semiconductor device according to Embodiment 1 of the present invention;

[0107]FIG. 14 is a fragmentary cross-sectional view of a substrate illustrating the manufacturing method of the semiconductor device according to Embodiment 1 of the present invention;

[0108]FIG. 15 is a fragmentary cross-sectional view of a substrate illustrating the manufacturing method of the semiconductor device according to Embodiment 1 of the present invention;

[0109]FIG. 16 is a fragmentary cross-sectional view of a substrate illustrating the manufacturing method of the semiconductor device according to Embodiment 1 of the present invention;

[0110]FIG. 17 is a fragmentary cross-sectional view of a substrate illustrating the manufacturing method of the semiconductor device according to Embodiment 1 of the present invention;

[0111]FIG. 18 is a fragmentary cross-sectional view of a substrate illustrating the manufacturing method of the semiconductor device according to Embodiment 1 of the present invention;

[0112]FIG. 19 is a fragmentary cross-sectional view of a substrate illustrating the manufacturing method of the semiconductor device according to Embodiment 1 of the present invention;

[0113]FIG. 20 is a fragmentary cross-sectional view of a substrate illustrating the manufacturing method of the semiconductor device according to Embodiment 1 of the present invention;

[0114]FIG. 21 is a fragmentary plane view of a substrate illustrating the manufacturing method of the semiconductor device according to Embodiment 1 of the present invention;

[0115]FIG. 22 is a fragmentary plane view of a substrate illustrating the manufacturing method of the semiconductor device according to Embodiment 1 of the present invention;

[0116]FIG. 23 is a fragmentary plane view of a substrate illustrating the manufacturing method of the semiconductor device according to Embodiment 1 of the present invention;

[0117]FIG. 24 is a fragmentary cross-sectional view of a substrate illustrating the manufacturing method of a semiconductor device according to Embodiment 2 of the present invention;

[0118]FIG. 25 is a fragmentary cross-sectional view of a substrate illustrating the manufacturing method of the semiconductor device according to Embodiment 2 of the present invention;

[0119]FIG. 26 is a fragmentary cross-sectional view of a substrate illustrating the manufacturing method of a semiconductor device according to Embodiment 3 of the present invention;

[0120]FIG. 27 is a fragmentary cross-sectional view of a substrate illustrating the manufacturing method of a semiconductor device according to Embodiment 4 of the present invention;

[0121]FIG. 28 is a fragmentary cross-sectional view of a substrate illustrating the manufacturing method of a semiconductor device according to Embodiment 5 of the present invention;

[0122]FIG. 29 is a fragmentary cross-sectional view of a substrate illustrating the manufacturing method of a semiconductor device according to Embodiment 6 of the present invention;

[0123]FIG. 30 is a fragmentary cross-sectional view of a substrate illustrating the manufacturing method of a semiconductor device according to Embodiment 6 of the present invention;

[0124]FIG. 31 is a fragmentary cross-sectional view of a substrate illustrating the manufacturing method of a semiconductor device according to Embodiment 7 of the present invention;

[0125]FIG. 32 is a fragmentary cross-sectional view of a substrate illustrating the manufacturing method of a semiconductor device according to Embodiment 8 of the present invention;

[0126]FIG. 33 is a fragmentary plane view of a substrate illustrating the manufacturing method of a semiconductor device according to Embodiment of the present invention;

[0127]FIG. 34 is a fragmentary cross-sectional view of a substrate illustrating the manufacturing method of a semiconductor device according to Embodiment of the present invention;

[0128]FIG. 35 is a fragmentary plane view of a substrate illustrating the manufacturing method of a semiconductor device according to Embodiment 9 of the present invention;

[0129]FIG. 36 is a fragmentary cross-sectional view of a substrate illustrating the manufacturing method of the semiconductor device according to Embodiment 9 of the present invention;

[0130]FIG. 37 is a fragmentary cross-sectional view of a substrate illustrating the manufacturing method of a semiconductor device according to Embodiment 6 of the present invention; and

[0131]FIG. 38 is a fragmentary cross-sectional view of a substrate illustrating the manufacturing method of a semiconductor device according to Embodiment 7 of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0132] The embodiments of the present invention will next be described in detail based on accompanying drawings. In all the drawings for describing the below-described embodiments, members having like function will be identified by like reference numerals and overlapping descriptions will be omitted.

[0133] (Embodiment 1)

[0134] A semiconductor device according to the embodiment of the present invention will be described in the order of its fabrication steps. FIGS. 1 to 23 are fragmentary cross-sectional or fragmentary plane views of a substrate illustrating the manufacturing method of a semiconductor device according to Embodiment 1 of the present invention.

[0135] As illustrated in FIG. 1, an n channel type MISFET (Metal Insulator Semiconductor Field Effect Transistor) Qn is formed over the main surface of a semiconductor substrate as one example of a semiconductor element.

[0136] The following is one example of an MISFET formation process.

[0137] First, prepared is a semiconductor substrate 1, so-called SOI (silicon on Insulator) substrate, which has an insulating film, for example, a silicon oxide film 1 b formed over a semiconductor region 1 a and further, a p type semiconductor region 1 c formed over the insulating film. Each element formation region of this semiconductor substrate (semiconductor region 1 c) is isolated by element isolations 2. These element isolations 2 can be formed by thermal oxidation of the semiconductor region 1 c or by embedding a silicon oxide film in an element isolation trench formed in the semiconductor region 1 c. By these regions in which these element isolations 2 have been formed, an active region in which a semiconductor element such as MISFET is to be formed is defined.

[0138] By thermal oxidation of the semiconductor substrate (which will hereinafter be called “substrate” simply) 1, a clean gate insulating film 8 is formed on the surface thereof.

[0139] Over the gate insulating film 8, a low-resistance polycrystalline silicon film 9 a, a thin WN (tungsten nitride) film 9 b and a W (tungsten) film 9 c are successively deposited as a conductive film.

[0140] The W film 9 c, WN film 9 b and polycrystalline silicon film 9 a are then etched utilizing, for example, a dry etching technique, whereby a gate electrode having the polycrystalline silicon film 9 a, WN film 9 b and W film 9 c is formed.

[0141] By ion implantation of, as an n type impurity, phosphorous (P) or arsenic (As) to the substrate 1 on both sides of the gate electrode 9, n⁻ type semiconductor regions 11 are formed.

[0142] After deposition of a silicon nitride film, as an insulating film, over the substrate 1, anisotropic etching is conducted to form side wall spacers 13 on the side walls of the gate electrode 9.

[0143] Then, ion implantation of an n type impurity to the substrate 1 on both sides of the gate electrode 9 is conducted to form n⁺ type semiconductor regions 14 (source, drain) having an impurity concentration higher than that of the n⁻ type semiconductor regions 11.

[0144] By the above-described steps, an n channel type MISFETQn having an LDD (Lightly Doped Drain) structure and equipped with a source and a drain is formed. A p channel type MISFETQp may be formed in a similar manner except that the impurity employed for the formation has the opposite conductivity.

[0145] Interconnects for electrically connecting the n channel type MISFETQn or another unillustrated element are then formed. Steps for forming them will next be described.

[0146] After formation of a silicon oxide film 20 as an insulating film over the n channel type MISFETQn by CVD (Chemical Vapor Deposition) as illustrated in FIG. 1, the surface of the silicon oxide film 20 is polished by chemical mechanical polishing (CMP) to planarize the surface.

[0147] A photoresist film (not illustrated, which will hereinafter be called “resist film” simply) is formed over the silicon oxide film 20. With this resist film as a mask, the silicon oxide film 20 is etched to form a contact hole C1 over the gate electrode 9 of the n channel type MISFETQn.

[0148] Over the silicon oxide film 20 in the contact hole C1, a titanium nitride (TiN) film P1 a is formed thin as a barrier metal layer by CVD or sputtering, followed by formation of a tungsten (W) film P1 b as a conductive film by CVD. The TiN film P1 a and W film P1 b outside the contact hole C1 is removed by CMP to form a plug P1. As the barrier metal layer, a laminate of a titanium (Ti) film and a TiN film may be employed.

[0149] As illustrated in FIG. 2, a silicon oxide film 22 a is formed as an insulating film by CVD over the silicon oxide film 20 and plug PI by using tetraethoxysilane as a raw material. This silicon oxide film 22 a will hereinafter be called “TEOS film 22”. FIG. 2 is a partially enlarged view illustrating the vicinity of the plug 1 illustrated in FIG. 1. The line in the plug P1 (P1 b) is a seam which appears upon deposition of the tungsten film.

[0150] Over the TEOS film 22 a, a low dielectric constant insulating film 22 b is then formed. This low dielectric constant insulating film can be formed by applying an aromatic polymer material, followed by heat treatment. Alternatively, an organic silica glass may be used for the low dielectric constant insulating film. Also in this case, heat treatment follows application of the material. This organic silica glass is composed mainly of SiOCH or SiOH. Another organic polymer material or the above-described material having pores introduced therein may be used.

[0151] Application of such a film as the low dielectric constant insulating film enables planarization of the unevenness on the substrate surface. The unevenness on the substrate surface derives from the uneven pattern of the underlying layer, or erosion or dishing upon CMP.

[0152] Alternatively, the low dielectric constant insulating film can be formed by CVD. For the formation, trimethylsilane or tetramethylsilane is used as a raw material. In this case, the film is composed mainly of SiOC. Examples of the low dielectric constant insulating film usable here include a film composed mainly of SiOF, a film composed mainly of SiC, and an organic polymer film (a film containing C and H) having an aromatic hydrocarbon structure. The dielectric constant can be decreased by introducing pores in (making porous) the above-described films or an SiO₂ (silicon oxide) film. These films can be formed by CVD.

[0153] Such a low dielectric constant insulating film has a dielectric constant (3.7 or lower) lower than that of a silicon oxide film (for example, TEOS film) so that it is possible to reduce a parasitic capacitance between interconnects (including gate electrodes) and speed up the operation of the semiconductor device.

[0154] Instead of the TEOS film 22 a, the above-described low dielectric constant insulating film (SiOC, SiOF, SiOC or a porous material of SiO₂) formed by CVD may be employed.

[0155] Over the low dielectric constant insulating film 22 b, a TEOS film 22 c is formed. The TEOS film 22 c is formed in a similar manner to the TEOS film 22 a.

[0156] The low dielectric constant insulating film 22 b is sandwiched between the TEOS films 22 a and 22 c in order to maintain the mechanical strength of the laminate of them. A wiring trench is formed in three layers, that is, TEOS films 22 a and 22 c, and low dielectric constant insulating film 22 b constituting an insulating film (22).

[0157] A wiring trench HM1 is then formed as illustrated in FIG. 3 by removing the insulating film 22 (22 a, 22 b, 22 c) by photolithography and dry etching from a region in which a first-level interconnect is to be formed. The wiring trench HM1 has, for example, a thickness of 0.25 μm and a width of 0.18 μm. This wiring trench HM1 can be formed with good controllability if an etching selectivity between the low dielectric constant insulating film 22 b and the TEOS film 22 a is utilized for the above-described etching using the TEOS film 22 a as an etching stopper film.

[0158] As illustrated in FIG. 4, a barrier film M1 a having a tantalum nitride (TaN) film and a tantalum (Ta) film stacked in the order of mention is formed by deposition over the insulating film 22 including the inside of the wiring trench HM1 by sputtering. This barrier film M1a may be formed by CVD or ionized sputtering which is one of sputtering. In this ionized sputtering, a metal constituting the barrier film is ionized and the metal ions are imparted with directivity by the biasing of the substrate. This makes it possible to deposit a film with good covering property even inside of a minute trench. The barrier film M1a is formed to have a thickness of about 5 nm on the side walls of the wiring trench HM1 and about 30 nm on its bottom.

[0159] The barrier film is not limited to the above-described laminate film of TaN and Ta. Examples of the film usable as the barrier film instead include a single-layer film made of Ta, TaN, TaSiN, W, tungsten nitride (WN), WsiN, Ti, TiN or TiSiN, a three-layer film of Ti, TiN and Ti, a two-layer film of Ti and TiN, a two-layer film of TiSiN and Ta, a three layer film of Ta, TaN and Ta, and a two-layer film of Ta and TaN. A laminate film obtained by stacking any two or more of these single-layer films may be employed.

[0160] Over the barrier film M1 a, a conductive film such as copper film is formed, for example, by electroplating. First, a thin copper film M1 b is formed as a seed film for electroplating, for example, by ionized sputtering. In this ionized sputtering, copper is ionized and then, the substrate is biased to impart the resulting copper ions with directivity. Upon deposition to form the copper film M1 b, the distance between the target and the substrate is kept at about 300 nm and the substrate temperature is adjusted to 25° C. or less. In the initial stage of the film formation, a relatively small DC or RF bias is applied to the substrate. After deposition of a certain thickness of a copper film over the substrate, the bias applied to the substrate is increased relatively. By an increase in the bias, the ions are injected to the substrate surface and the copper film already deposited thereover is sputter etched. At this time, the ions are injected substantially perpendicularly relative to the substrate so that the plane parts (insulating film 22 and the bottom of the wiring trench HM1) are etched preferentially. Copper which has scattered is re-deposited on the side walls of the wiring trench HM1, thereby improving the step coverage of the side walls and bottom of the wiring trench HM1. For the film formation, low-pressure long-distance sputtering is replaced for the ionized sputtering.

[0161] A copper film M1 c is formed over the copper film M1 bby electroplating using, for example, a copper-sulfate-containing solution as a plating solution. This copper film M1 c is formed so as to embed therewith the wiring trench HM1.

[0162] Under a reducing atmosphere, the substrate 1 is annealed (heat treated). As illustrated in FIG. 5, the copper films M1 c and M1 b and the barrier film M1 b outside the wiring trench HM1 are removed, for example, by CMP or etchback to form a first-level interconnect M1 composed of the copper films M1 b and M1 c and barrier film M1 a. Then, the substrate is annealed (heat treated) further under a reducing atmosphere.

[0163] As illustrated in FIG. 6, a tungsten film CM1 of about 2 to 20 nm thick is formed over the first-level interconnect M1 by causing selective growth or preferential growth of tungsten (W) thereover. The tungsten film CM1 is formed, for example, by the treatment for 1.5 minutes under the following conditions: 0.3 Torr (0.3×1.33322×10² Pa), susceptor temperature set at 460° C. (actual substrate temperature: 430° C.), a flow rate of tungsten hexafluoride (WF₆): 5 cc, and a hydrogen (H₂) flow rate: 500 scc.

[0164] By the above-described treatment, tungsten selectively grows only over the first-level interconnect M1 or grows preferentially over the first-level interconnect M1 to the TEOS film 22. The treatment is conducted at a relatively high temperature while giving priority to the growth rate of tungsten, but the temperature may be set at about 300° C. Thus, a capping conductive film can be formed conveniently by using either one of selective growth or preferential growth. Although 1) a tungsten film, after formed all over the surface of the substrate, may be patterned by photolithography or dry etching; or 2) a capping conductive film may be formed by over polishing or over etching of the surface of the copper film upon CMP or etch back, thereby concaving the surface of the copper film, and embedding a tungsten film in this concave (which means, the tungsten film outside the concave is removed by CMP or the like after formation of the tungsten film all over the surface), such a method makes the fabrication step complicated. In addition, misalignment upon photolithography or dishing or erosion upon CMP must be controlled, making it difficult to form the capping conductive film with precision. If selective growth or preferential growth is adopted, on the other hand, the fabrication step does not become complicated and the capping conductive film can be formed with good precision. It is needless to say that the method for forming the capping conductive film is not limited to selective growth or preferential growth; and that for the formation of the capping conductive film, not only CVD but also plating can be employed.

[0165] As the capping conductive film over the first-level interconnect M1, a metal layer composed mainly of W, or a single-layer film of WN, WSiN, TiN, TiSiN, Ta, TaN, or TaSiN (tantalum silicide nitride), a metal layer composed mainly of Co, CoWP (cobalt tungsten phosphorous), CoWB (cobalt tungsten boron), or a laminate (two-layer film or three-layer film) obtained by stacking any plural films of them may be used as well as tungsten film. Tungsten has a resistance of 5 to 20 μΩ, while TiN has a resistance of 80 to 150 μΩ. Ta or TaN is also higher in resistance than tungsten. Use of tungsten as the capping conductive film can therefore reduce the resistance of an interconnect compared with the use of another film. It is to be noted that copper has a resistance of 1.7 to 2.2 μΩ.

[0166] Annealing just before the formation of the tungsten film CM1 and formation of the tungsten film CM1 may be conducted in the same apparatus (in situ). When film formation and annealing are conducted in a multi-chamber having therein both a film forming apparatus and an annealing apparatus without taking the substrate out of the chamber, the surface of the substrate (copper film M1 c) can be prevented from contamination, leading to improvements in the film forming property and film quality of the tungsten film.

[0167] Prior to the formation of the tungsten film CM1, contamination of copper on the substrate surface after CMP may be removed by washing with a cleaning solution such as hydrogen fluoride (HF). Such washing improves selectivity of the tungsten film. Here, washing with hydrogen fluoride is given as an example, but the cleaning solution is not limited to hydrogen fluoride insofar as it has an etching capacity of the surface of the insulating film exposed from the substrate surface or a capacity of removing copper contamination adhered to the surface. Similar effects to the above-described washing are available when the substrate 1 is exposed to the atmosphere of hydrogen (H₂) flow rate of 500 cm³/min (sccm) (for example, 50 to 3000 sccm) under pressure of, for example, 3000 Pa (for example, 150 to 10000 Pa) for three minutes prior to the formation of the tungsten film CM1. By eliminating the copper contamination or reducing the oxide on the copper surface to copper by hydrogen treatment, the tungsten film is able to have improved selectivity, a short circuit between interconnects due to loss of selectivity can be prevented, and uniformity of the thickness of the tungsten film formed over an interconnect (copper film) can be improved. Since the oxide of copper will serve as a supply source of copper ions upon electrodiffusion, removal of such an oxide makes it possible to reduce the injection amount of copper ions into the insulating film and improve the reliability of the semiconductor device.

[0168] When the tungsten film inevitably grows on the TEOS film 22, the tungsten film on the insulating film can be removed by the lift-off effect brought by the above-described washing-off of copper. The composition of the cleaning solution is not limited insofar as it has a capacity of etching the surface of the insulating film exposed from the substrate surface or having a capacity of removing tungsten adhered to the surface. It is also possible to remove the unnecessary tungsten film on the insulating film by light CMP or post-washing of the substrate surface after formation of the tungsten film. Removal of a conductive substance on the TEOS film 22 c can prevent a short circuit between interconnects.

[0169] As illustrated in FIG. 7, then, a TEOS film 24 a, an SiOC film 24 b and a TEOS film 24 c are successively deposited as an insulating film by CVD over the TEOS film 22 c and tungsten film CM1. These films have unevenness on their surfaces corresponding to the unevenness of the tungsten film CM1. By the TEOS film 24 a and SiOC film 24 b of this laminate film (24), the first-level interconnect M1 is insulated from the second-level interconnect M2. In these films, a contact hole C2 for forming a plug (connecting portion) P2 which connects the first-level interconnect M1 and the second-level interconnect M2 is formed. Instead of the TEOS films 24 a and 24 c, a TMS film, SiC film or SiCN film which is a barrier insulating film having a low dielectric constant relative to the SiN film (silicon nitride film) may be used. Such a low dielectric constant insulating film can be formed, for example, by the following manner. A TMS film can be formed using trimethoxysilane and dinitrogen monoxide (N₂O) by CVD. It is composed mainly of SiON (a film composed mainly of SiON is called “TMS film”). An SiC film can be formed using trimethylsilane, while an SiCN film can be formed using trimethylsilane and ammonia. Another low dielectric constant film may be employed instead of the TEOS film 24 a or 24 c. Instead of the SiOC film 24 b, an SiOF film may be employed.

[0170] As illustrated in FIG. 8, a low dielectric constant insulating film 26 b using a coating material such as aromatic polymer material and a TEOS film 26 c are then successively formed, as an insulating film, over the TEOS film 24. These films (26 b, 26 c) are formed in a similar manner to that employed for the formation of the low dielectric constant insulating film 22 b and TEOS film 22 c. The unevenness of the substrate surface can be planarized because a coated film is used as the low dielectric constant insulating film. In addition, the low dielectric constant insulating film 26 b is sandwiched between the TEOS films 26 c and 24 c so that the mechanical strength of the laminate film (26) of these films can be maintained. In the insulating film (26) and the above-described TEOS film 24 c, a wiring trench HM2 to be embedded with the second-level interconnect M2 is formed.

[0171] As illustrated in FIG. 9, a hard mask MK is deposited over the TEOS film 26 c, followed by removal of the hard mask MK from a second-level interconnect formation region by photolithography and dry etching. As the hard mask MK, a silicon nitride film or the like can be employed.

[0172] As illustrated in FIG. 10, a resist film RI is formed over the hard mask MK. The resist film RI is then removed by photolithography from a connecting region of the first-level interconnect and the second-level interconnect.

[0173] With this resist film R1 as a mask, the TEOS film 24 c and SiOC film 24 b, among the insulating film 26 (26 b and 26 c) and the insulating film 24, are removed, for example, by dry etching to form the contact hole C2. The TEOS film 24 a is thus left on the first-level interconnect M1 in order to prevent oxidation of exposed copper which will otherwise occur upon ashing for the removal of the resist to be conducted later, and to prevent scattering of copper upon dry etching. It is however not essentially necessary to leave the TEOS film 24 over the first-level interconnect M1, because the copper film M1C is covered with the tungsten film CM1 serving as a capping conductive film.

[0174] As illustrated in FIG. 11, after removal of the resist film RI, a wiring trench HM2 is formed by removing the insulating film 26 (26 b and 26 c) and the TEOS film 24 c, for example, by dry etching with the hard mask MK as a mask. At this time, the TEOS film 24 a remaining on the bottom of the contact hole C2 is also removed.

[0175] This wiring trench HM2 has a thickness of about 0.25 μm and a width of about 0.18 μm. The contact hole C2 has a depth of about 0.35 μm from the bottom of the wiring trench HM2 and its diameter is about 0.18 μm.

[0176] Here, the wiring trench HM2 is formed after formation of the contact hole C2. Alternatively, the contact hole C2 may be formed after the formation of the wiring trench HM2 and then embedding a resist film or the like in this trench to planarize the substrate surface.

[0177] As illustrated in FIG. 12, the tungsten film CM1 exposed from the bottom of the contact hole C2 is removed, for example, by dry etching to expose the copper film M1 c. Although no particular limitation is imposed, the formation of the wiring trench HM2 and dry etching for the removal of the tungsten film CM1 can be conducted successively by changing the kind of the etching gas used therefor.

[0178] Since the tungsten film CM1 exposed from the bottom of the contact hole C2 can be removed utilizing the steps of forming the contact hole C2 and wiring trench HM2, it can be removed selectively without adding a step for the formation of another mask. The hard mask MK is then removed.

[0179] The oxide on the copper film M1 c exposed from the bottom of the contact hole is then removed by using the following treatments singly or in combination: heat treatment in an atmosphere containing hydrogen or ammonia, exposure of the substrate surface to plasma generated in an atmosphere containing hydrogen, ammonia or a mixture of either one of hydrogen or ammonia and a rare gas such as Ar, and sputter etching of the substrate surface with a rare gas such as Ar. Then, as illustrated in FIG. 13, a barrier film PM2 a having, for example, a tantalum nitride (TaN) film and tantalum (Ta) film stacked in the order of mention is deposited over the TEOS film 26 including the insides of the wiring trench HM2 and contact hole C2, for example, by low-pressure long-distance sputtering. The barrier film PM2 a may be formed by CVD, or by ionized sputtering which was described specifically in the formation step of the copper film M1 b. As described above, the ionized sputtering can impart deposited metal ions with directivity. In the latter stage of film formation, when a metal deposited on the wiring trench or bottom of the contact hole is sputter-etched under a large bias, the metal thus scattered can be re-deposited over the side walls thereof, whereby step coverage of the side walls and bottom can be improved.

[0180] Here, the thickness of the barrier film PM2 a is adjusted to about 5 nm on the side walls of the wiring trench HM2, about 30 nm on the bottom of the wiring trench HM2, about 3 nm on the side walls of the contact hole C2 and about 20 nm on the bottom of the contact hole C2. By controlling the film thickness of the barrier film PM2 a on the bottom of the wiring trench HM2 to be greater than that on the bottom of the contact hole C2, the barrier film PM2 a can be left on the bottom of the wiring trench HM2 even if the barrier film PM2 a is removed later from the bottom of the contact hole C2 by sputter etching. Moreover, by forming the barrier film PM2 a while setting the initial film forming conditions to permit high anisotropy (directivity), it is possible to prevent excessive thickening of the barrier film PM2 a on the bottom or side walls of the wiring trench HM2 or on the side walls of the contact hole C2.

[0181] As illustrated in FIG. 14, the barrier film PM2 a is removed from the bottom of the contact hole C2, followed by formation of a copper film PM2 b over the barrier film PM2 a and exposed copper film M1 c. The removal of the barrier film PM2 a and formation of the copper film PM2 b can be conducted, for example, by the above-described ionized sputtering.

[0182] While the distance between the target and substrate is set at about 300 mm and the substrate temperature is adjusted to 25° C. or less, the barrier film PM2 a on the bottom of the contact hole C2 is sputter etched by applying a large DC or RF bias to the substrate at an initial stage, thereby injecting copper ions and argon (Ar) ions, contained in the atmosphere, to the substrate surface. At this time, these ions are incident to the substrate substantially perpendicularly so that the plane portion (the bottom of the wiring trench HM2 and the bottom of the contact hole C2) is etched preferentially. As described above, the barrier film PM2 a on the bottom of the wiring trench HM2 is made thicker than that on the bottom of the contact hole C2 so that it is possible to leave the barrier film PM2 a on the bottom of the wiring trench HM2 while removing the barrier film PM2 a on the bottom of the contact hole C2.

[0183] By selecting the etching conditions properly, thereby re-depositing the scattered barrier film PM2 a on the side walls and bottom of the wiring trench HM1 or contact hole C2, the step coverage of these side walls or bottom can be improved. It is also possible to even out the thickness of the barrier film PM2 a on the side walls of the wiring trench HM2 or contact hole C2 by re-depositing the barrier film PM2 a which has deposited thick on the upper portion (corner) of the side walls of the wiring trench HM2 or the contact hole C2.

[0184] A thin copper film PM2 b is deposited, as a seed film for electroplating, in the wiring trench HM2 and contact hole C2 as illustrated in FIG. 15 by reducing a bias or terminating application of a bias. At this time, as described above, it is possible to improve step coverage of the copper film PM2 b on the side walls and bottom of the wiring trench HM2 or contact hole C2 by increasing a bias to a relatively high level after deposition of a certain thickness of the copper film over the substrate.

[0185] As a result, the copper film PM2 b is formed via the barrier film PM2 a over the side walls and bottom of the wiring trench HM2 and the side walls of the contact hole C2, while over the copper film M1 c exposed from the bottom of the contact hole C2, the copper film PM2 b is formed directly without insertion of the barrier film PM2 a therebetween. The barrier film PM2 a has a thickness of about 5 nm on the side walls and bottom of the wiring trench HM2, and about 3 nm on the side walls of the contact hole C2, while the copper film PM2 b has a thickness of about 10 nm.

[0186] If removal of the barrier film PM2 a from the bottom of the contact hole C2 and formation of the copper film PM2 b inside of the wiring trench HM2 and contact hole C2 are carried out in one apparatus, oxidation of the barrier film PM2 a or adhesion of the foreign matters thereto can be prevented and quality of each of the barrier film PM2 a and copper film PM2 b can be improved. It is also possible to form the copper film PM2 b on another site (inside of the wiring trench HM2 or over the side walls of the contact hole C2) while removing the barrier film PM2 a from the bottom of the contact hole C2 under the conditions such as bias changed as needed.

[0187] The removal of the barrier film PM2 a from the bottom of the contact hole C2 and formation of the copper film PM2 b inside of the wiring trench HM2 and contact hole C2 may be conducted in respective apparatuses. For example, after removal of the barrier film PM2 a from the bottom of the contact hole C2 by anisotropic etching, the copper film PM2 b may be formed inside of the wiring trench HM2 and contact hole C2 by sputtering. In this case, heat treatment or plasma treatment in a reducing atmosphere containing hydrogen or ammonia, or washing with a cleaning solution such as hydrogen fluoride (HF) may be conducted in order to remove the oxide or foreign matters on the surfaces of the barrier film PM2 a and the copper film M1 c exposed by anisotropic etching.

[0188] A copper film PM2 c is then formed over the copper film PM2 b by electroplating using, as a plating solution, a copper-sulfate-containing solution. This copper film PM2 c is formed so as to embed therewith the wiring trench HM2 and contact hole C2.

[0189] After annealing (heat treating) of the substrate 1 in a reducing atmosphere, the copper films PM2 c and PM2 b, and the barrier film PM2 a outside the wiring trench HM2 and contact hole C2 are removed by CMP or etchback, whereby a second-level interconnect M2 and a plug (connecting portion) P2 for connecting the first-level interconnect M1 with the second-level interconnect, each made of the copper films PM2 b and PM2 c and barrier film PM2 a, are formed as illustrated in FIG. 16. Here, the second-level interconnect M2 means the copper films PM2 b and PM2 c and barrier film PM2 a embedded inside of the wiring trench HM2, while the plug P2 means the copper films PM2 b and PM2 c and barrier film PM2 a embedded inside of the contact hole C2 extending from the bottom of the wiring trench HM2.

[0190] In a reducing atmosphere, the substrate 1 is annealed (heat treated) further.

[0191] As described above, this embodiment actualizes a reduction in resistance, because the tungsten film CM1 and barrier film PM2 a between the first-level interconnect M1 and plug P2 are removed and the first-level interconnect M1 is in direct contact with copper which is a main metal constituting the plug P2. Moreover, this embodiment enables movement of copper atoms between the first-level interconnect M1 and plug P2, which makes it possible to diminish a generation ratio of voids at the interface between the first-level interconnect M1 and plug P2, thereby improving electromigration resistance.

[0192] Described specifically, neither the barrier film PM2 a nor tungsten film CM1 is formed on the bottom of the contact hole C2, that is, at a joint between the first-level interconnect M1 and plug (connecting portion) P2. Since both the barrier film PM2 a and tungsten film CM1 are removed from the bottom of the contact hole C2, the first-level interconnect M1 is in direct contact with copper which is a main metal constituting the plug P2. No interface exists between the barrier metal and copper so that disconnection in the vicinity of the plug due to stress migration can be prevented.

[0193] Since the tungsten film CM1 and barrier film PM2 a are integrated (these films cover the copper film without interruption), the whole surface of the copper film inside thereof is covered with the barrier metal film. An interface between copper having a relatively low adhesion property and an insulating film can be eliminated from the structure, which brings about an improvement in the adhesion on the surface of copper. As a result, generation of voids can be suppressed and electromigration resistance can be improved.

[0194] Although neither the tungsten film CM1 nor the barrier film PM2 a exist between the tungsten film CM1 and barrier film PM2 a, another portion of the first-level interconnect M1 and plug P2 is covered with the tungsten film CM1 or barrier film PM2 a. This structure makes it possible 1) to prevent diffusion, into the insulating film, of a metal (copper in the case of a copper film) constituting the conductive film to be embedded, and 2) to prevent oxidation of the conductive film owing to the contact of the silicon oxide film with the conductive film.

[0195] The use of a tungsten film as the capping conductive film makes it possible to improve electromigration resistance, compared with the use of an insulating film such as silicon nitride film as the capping film, because copper does not diffuse easily on the copper-barrier film interface than the copper-silicon nitride film interface.

[0196] In addition, an effective dielectric constant of the insulating film existing between interconnects can be reduced because an insulating film such as silicon nitride film is not used as the capping conductive film. As a result, the transmission speed of signals via interconnects can be improved and high-speed operation of a semiconductor device can be actualized. The dielectric constant of the silicon nitride film is approximately 6 to 8, while that of the TEOS film is 4.

[0197] The first-level interconnect M1 and plug P2 are covered with the hard tungsten film CM1 or barrier film PM2 a, breakage of the interconnect due to stress migration can be prevented. Such a stress occurs, for example, owing to heat stress applied upon heat treatment. Particularly in this Embodiment, since a low dielectric constant insulating film which has low hardness is employed, protection of the first-level interconnect M1 and plug P2 is effective.

[0198] Since a tungsten film is used as the capping conductive film, it can be embedded in a defect, if any, appearing on the surface of the underlying copper film, leading to an improvement in the reliability of the interconnect and also in the yield of the product. The defect on the surface of the copper film is caused by breakage, shrinkage or scratches. For example, breakage or scratches occur upon polishing of the copper film by CMP. They also occur by the heat treatment or insufficient embedding of the copper film.

[0199] If such a defect causes a clearance in the copper film or at the interface between the copper film and barrier film, an interconnect resistance increases. Such a clearance becomes a starting point of electromigration, thereby lowering electromigration resistance. A plug formed over such a clearance inevitably heightens a connection resistance.

[0200] Use of a tungsten film as the capping conductive film, on the other hand, can repair the clearance by embedding therein the tungsten film, thereby improving electromigration resistance, reliability of the resulting semiconductor device, and moreover, the yield of the product.

[0201] As illustrated in FIG. 17, a tungsten film CM2 of about 2 to 20 nm thick is then formed over the second-level interconnect M2 (PM2 c) by selective growth or preferential growth of tungsten (W) over the second-level interconnect M2. This tungsten film CM2 is formed, for example, by the treatment for 1.5 minutes under the following conditions: 0.3 Torr (0.3×1.33322×10² Pa), susceptor preset temperature of 460° C. (actual substrate temperature: 430° C.) flow rate of tungsten hexafluoride (WF₆) of 5 scc, and flow rate of hydrogen (H₂) of 500 scc.

[0202] The above-described treatment causes selective growth of tungsten only over the second-level interconnect M2 or preferential growth of tungsten over the second-level interconnect M2 compared to the growth over the TEOS film 26 c. The above treatment is conducted at a relatively high temperature while giving priority to the growth rate of tungsten, but the temperature may be set at about 300° C.

[0203] As the capping conductive film, not only tungsten but also a single layer film of WN, WSiN, CoWP, CoWB, TiN, TiSiN, Ta, TaN or TaSiN or a laminate film (two-layer film, three-layer film, etc.) obtained by stacking any two or more of these films may be used.

[0204] As described above, annealing just before the formation of the tungsten film CM2 and formation of the tungsten film CM2 may be conducted in one apparatus (in situ).

[0205] Prior to the formation of the tungsten film CM2, contamination of copper on the substrate surface after CMP may be removed, for example, by washing with a cleaning solution such as hydrogen fluoride (HF) or treatment for 3 minutes in an atmosphere of hydrogen (H₂) flow rate of 500 cm³/min (sccm) under pressure of 3000 Pa.

[0206] The tungsten film which has grown on the TEOS film 26 c can be removed by the lift-off effect brought by the above-described washing of copper. It is also possible to remove the tungsten film on the TEOS film 26 c by light CMP of the substrate surface after formation of the tungsten film. Removal of a conductive substance on the TEOS film 26 c in such a manner can prevent a short circuit between interconnects.

[0207] As illustrated in FIG. 18, a TEOS film 28 a, an SiOC film 28 b and another TEOS film 28 c are deposited successively by CVD over the TEOS film 26 c and tungsten film CM2. These films are formed in a similar manner to that employed for the formation of the TEOS films 24 a and 24 c, and SiOC film 24 b. Over the TEOS film 28 c, a low dielectric constant insulating film 30 b using an aromatic polymer material and a TEOS film (not illustrated) are formed successively as an insulating film. These films are formed in a similar manner to that employed for the formation of the low dielectric constant insulating film 22 b and TEOS film 22 c.

[0208] In the resulting 5-layer insulating film, a wiring trench and contact hole are formed in a similar manner to that employed for the wiring trench HM2 and contact hole C2. The formation step of them is not illustrated.

[0209] Formation of an insulating film, wiring trench, contact hole, barrier film, copper film and tungsten film in such a manner is repeated, whereby a semiconductor device having a multilayer interconnect is formed.

[0210]FIGS. 19 and 20 illustrate one example of a 5-layer interconnect (M1 to M5). FIGS. 21 to 23 are fragmentary plane view of the semiconductor device shown in FIGS. 19 and 20, in which FIG. 19 corresponds to the A-A′ cross-section, while FIG. 20 corresponds to the B-B′ cross-section. FIG. 21 is a plane view clearly showing the disposition of the first-level interconnect M1 to fifth-level interconnect M5. In order to facilitate understanding of it, FIG. 22 illustrates the disposition of the first-level interconnect M1 to third-level interconnect M3, while FIG. 23 illustrates the disposition of the third-level interconnect M3 to fifth-level interconnect M5.

[0211] As illustrated in FIGS. 19 to 23, the third-level interconnect M3 and a plug P3 which lies thereunder can be formed in a similar manner to that employed for the second-level interconnect M2 and the plug 2 which lies thereunder.

[0212] Described specifically, after formation of a wiring trench (HM3) and contact hole (C3) in insulating films (28 and 30), a barrier film (PM3 a) and copper film (PM3 b and PM3 c) are successively formed over the insulating films including the insides of the wiring trench (HM3) and contact hole (C3). In the contact hole C3, a plug P3 is formed.

[0213] Upon formation of the contact hole (C3), the tungsten film (CM2) formed over the surface of the interconnect which lies under the contact hole is removed in advance. Prior to the formation of the copper film (PM3 b), the barrier film (PM3 a) is removed from the bottom of the contact hole (C3). It is also possible to remove the barrier film (PM3 a) from the bottom of the contact hole (C3) while forming the copper film (PM3 b).

[0214] As a result, effects as described above such as reduction in contact resistance between the interconnect (M3) and plug (P3) and improvement in electromigration resistance are available.

[0215] As illustrated in FIGS. 19 and 20, the third-level interconnect M3 is connected to the fourth-level interconnect M4 via a barrier film PM4 a and a tungsten film CM3, while the fourth-level interconnect M4 is connected to the fifth-level interconnect M5 via a barrier film PM5 a and a tungsten film CM4. As illustrated in FIGS. 21 and 23, the width of each of the third-level interconnect M3 to the fifth-level interconnect M5 is wide so that a large connecting region (diameter of the plug 4 or 5) can be secured. Even the barrier films (PM4 a, PM5 a) and tungsten films (CM3, CM4) exist, contact resistance can be suppressed to a relatively small level. By the omission of a step of removing these films from the connection region, the simplification of the step can be attained. With regards to the barrier film PM5 a constituting the fifth-level interconnect M5, is, for example, a TiN film, a two-layer film of Ti and TiN, or three-layer film of Ti, TiN and Ti; PM5 b is an aluminum (Al) or Al alloy film; and PM5 c thereover is a TiN film or a two-layer film of Ti and TiN. Over the fifth-level interconnect M5, a laminate film 38 of a silicon oxide film and a silicon nitride film is formed as a protective film.

[0216] As illustrated in FIGS. 19 and 20, the tungsten film CM5 over the fifth-level interconnect M5 may be formed thinner than the tungsten film CM4 over the fourth-level interconnect M4. By adjusting the tungsten film (second capping barrier metal film) over the fifth-level interconnect to be thinner than the tungsten film (first capping barrier metal film) over the fourth-level interconnect, a connection resistance with the upper-layer interconnect can be reduced. By forming the lower tungsten film to be thicker than the upper one, a margin of reliability can be maintained.

[0217] On the contrary, with regards to the tungsten films CM4, CM5 over the fourth-level interconnect M4 and fifth-level interconnect M5, the tungsten film CM4 may be formed thinner than the tungsten film CM5. A contact hole formed over the upper-layer interconnect usually has a large diameter so that an increase in the thickness of the tungsten film (second capping barrier metal film) over the upper-layer interconnect has no influence on connection resistance. By thickening the tungsten film over the upper-layer interconnect within an extent not affecting the connection resistance, the margin of reliability can be maintained. Since the layout rule of the upper-layer interconnect is not so severe, the possibility of short-circuit which may occur by thickening of the tungsten film can be reduced. Thinning of the tungsten film (first capping barrier metal film) over the lower-layer interconnect makes it possible to reduce the unevenness on the surface of the interconnect and reduce the possibility of short circuit between interconnects. Such unevenness becomes prominent as the number of layers to be stacked increases. If the surface of the interconnect becomes markedly irregular, it can be flattened using a coated film as the insulating film over the interconnect. The tungsten films CM4, CM5 over the fourth-level interconnect M4 and fifth-level interconnect M5 were so far described, which equally apply to the tungsten films CM3, CM4 over the third-level interconnect M3 and fourth-level interconnect M4, or the tungsten films CM2, CM3 over the second-level interconnect M2 and the third level-interconnect M3.

[0218] After formation of the laminate film 38, the substrate surface is subjected to NH₃ plasma treatment. This treatment causes 1) reduction of the surface of a copper film constituting the interconnects (M1 to M4) formed over the substrate, 2) nitriding of the surface of the copper film, 3) cleaning of the surface of the insulating film such as TEOS film formed over the substrate, 4) recovery from the damage of the surface of the insulating film, or 5) nitriding of the surface of the insulating film. As a result, ionization of copper constituting the interconnect can be suppressed. In addition, diffusion of copper ions in the insulating film can be prevented, whereby characteristics of the insulating film can be improved.

[0219] (Embodiment 2)

[0220] In this Embodiment, an example of the laminated structure of an insulating film in which a wiring trench and a contact hole are to be formed will be described.

[0221] (1) In Embodiment 1, the wiring trench HM2 and contact hole C2 were formed in a five-layer insulating film (24 a, 24 b, 24 c, 26 b, 26 c) (refer to FIG. 12), but of these films, 24 a may be omitted. FIG. 24 is a fragmentary cross-sectional view of a substrate illustrating the manufacturing method of a semiconductor device according to Embodiment 2 of the present invention.

[0222] The semiconductor device of this Embodiment of the present invention will next be described in accordance with its manufacturing method. The steps up to the formation of the first-level interconnect M1 and the tungsten film CM1 thereover are similar to those of Embodiment 1 which were described with reference to FIGS. 1 to 6 so that the description of them are omitted.

[0223] Then, as illustrated in FIG. 24, an SiOC film 24 b and a TEOS film 24 c are deposited, as an insulating film, successively over the TEOS film 22 c and tungsten film CM1 by CVD. Over the TEOS film 24 c, a low dielectric constant insulating film 26 b, by using a coating material such as aromatic polymer material, and a TEOS film 26 c are successively formed as an insulating film. The properties and shape of these four films (24 b, 24 c, 26 b, 26 c) were as described in detail in Embodiment 1.

[0224] In the SiOC film 24 b of these four films (24 b, 24 c, 26 b, 26 c), a contact hole C2 for the formation of a plug (connecting portion) P2 for connecting the first-level interconnect M1 and the second-level interconnect M2 is formed, while in the TEOS film 24 c, low dielectric constant insulating film 26 b and TEOS film 26 c, a wiring trench HM2 is formed.

[0225] As in Embodiment 1, a hard mask (not illustrated) having an opening in a second-level interconnect formation region is formed over the TEOS film 26, followed by the formation of a resist film (not illustrated) having an opening in a connecting region of the first-level interconnect with the second-level interconnect.

[0226] With the resist film as a mask, the insulating films 26 and 24 are removed to form the contact hole C2. After removal of the resist film, the insulating film 26 and TEOS film 24 are removed with the hard mask as a mask to form the wiring trench HM2. The contact hole C2 may be formed after the formation of the wiring trench HM2.

[0227] The tungsten film CM1 exposed from the bottom of the contact hole C2 is removed, for example, by dry etching to expose a copper film M1 c.

[0228] Steps on and after the formation of the second-level interconnect M2 and plug (connecting portion) P2 are similar to those in Embodiment 1 so that only their outline will next be described.

[0229] As in Embodiment 1, a barrier film PM2 a is formed over the TEOS film 26 including the insides of the wiring trench HM2 and contact hole C2. It is deposited to give a thickness of about 5 nm on the side walls of the wiring trench HM2, about 30 nm on the bottom of the wiring trench HM2, about 3 nm on the side walls of the contact hole C2 and about 20 nm on the bottom of the contact hole C2.

[0230] As in Embodiment 1, the barrier film PM2 a is removed from the bottom of the contact hole C2. After deposition of a thin copper film PM2 b as a seed film for electroplating, a copper film PM2 c is formed over the copper film PM2 b by electroplating. In a reducing atmosphere, the substrate 1 is annealed (heat treated), followed by removal of the copper films PM2 c and PM2 b and barrier film PM2 a outside the wiring trench HM2 and contact hole C2 by CMP or etchback, whereby a second-level interconnect M2 and a plug (connecting portion) P2 for connecting the first-level interconnect M1 and the second-level interconnect, each made of the copper films PM2 b, PM2 c and barrier film PM2 a, are formed.

[0231] As in Embodiment 1, selective growth or preferential growth of tungsten (W) is effected over the second-level interconnect M2, whereby a tungsten film CM2 is formed.

[0232] As illustrated in FIG. 24, an SiOC film 28 b and a TEOS film 28 c are then deposited successively, as an insulating film, by CVD over the TEOS film 26 c and tungsten film CM2. These films are similarly formed to the SiOC film 24 b and TEOS film 24 c. Over the TEOS film 28 c, a low dielectric constant insulating film 30 b, using a coating material such as aromatic polymer material, and a TEOS film (not illustrated) are successively formed as an insulating film. These films are formed similarly to the low dielectric constant insulating film 22 b and TEOS film 22 c.

[0233] In the above-described four-layer insulating film, a wiring trench and a contact hole are formed in a similar manner to that employed for the formation of the wiring trench HM2 and contact hole C2, but illustration of this step is omitted.

[0234] According to this Embodiment, the wiring trench HM2 and contact hole C2 are formed in the four-layer insulating film (24 b, 24 c, 26 b, 26 c) so that their formation step can be simplified compared with that in Embodiment 1.

[0235] Since the tungsten film CM1 and barrier film PM2 a between the first-level interconnect M1 and plug P2 are removed, contact resistance between the first-level interconnect M1 and plug P2 can be reduced and electromigration resistance can be improved. Thus, effects as described in Embodiment 1 are available.

[0236] (2) In Embodiment 1, the wiring trench HM2 and contact hole C2 were formed in the five-layer insulating film (24 a, 24 b, 24 c, 26 b, 26 c), however, the insulating film 26 c may be omitted from these five insulating films. FIG. 25 is a fragmentary cross-sectional view of a substrate illustrating the manufacturing method of a semiconductor device according to Embodiment 2 of the present invention.

[0237] The semiconductor device of this embodiment of the present invention will next be described in accordance with its manufacturing method. Steps up to the formation of the first-level interconnect M1 and the tungsten film CM1 thereover are similar to those described above in Embodiment 1 with reference to FIGS. 1 to 6, so that their description is omitted.

[0238] As illustrated in FIG. 25, a TEOS film 24 a, an SiOC film 24 b and another TEOS film 24 c are successively deposited by CVD as an insulating film over the substrate 1 (first-level interconnect M1). Then, over the TEOS film 24 c, a low dielectric constant insulating film 26 b is formed as an insulating film by using a coating material such as aromatic polymer material. The properties or shape of these four films (24 a, 24 b, 24 c, 26 b) are as described in detail in Embodiment 1.

[0239] In the SiOC film 24 b and TEOS film 24 a of these four films (24 a, 24 b, 24 c, 26 b), a contact hole C2 for the formation of a plug (connecting portion) P2 for connecting the first-level interconnect M1 with the second-level interconnect M2 is formed, while in the TEOS film 24 c and the low dielectric constant insulating film 26 b, a trench HM2 is formed.

[0240] As in Embodiment 1, a hard mask (not illustrated) having an opening in a second-level interconnect formation region is formed over the low dielectric constant insulating film 26 b, followed by the formation of a resist film (not illustrated) having an opening in a connecting region of the first-level interconnect with the second-level interconnect.

[0241] With the resist film as a mask, the low dielectric constant insulating film 26 b, TEOS film 24 c and SiOC film 24 b are removed to form the contact hole C2, followed by the removal of the resist film. With the hard mask as a mask, the low dielectric constant insulating film 26 b and TEOS film 24 c are removed to form the wiring trench HM2 and the TEOS film 24 a is removed from the bottom of the contact hole C2. The contact hole C2 may be formed after the formation of the wiring trench HM2.

[0242] The tungsten film CM1 exposed from the bottom of the contact hole C2 is removed, for example, by dry etching to expose a copper film M1 c (first-level interconnect M1).

[0243] Steps on and after the formation of the second-level interconnect M2 and plug (connecting portion) P2 are similar to those of Embodiment 1 so that only their outline will next be described.

[0244] As in Embodiment 1, a barrier film PM2 a is formed over the low dielectric constant insulating film 26 b including the insides of the wiring trench HM2 and contact hole C2. It is deposited to give a thickness of about 5 nm on the side walls of the wiring trench HM2, about 30 nm on the bottom of the wiring trench HM2, about 3 nm on the side walls of the contact hole C2 and about 20 nm on the bottom of the contact hole C2.

[0245] As in Embodiment 1, the barrier film PM2 a is removed from the bottom of the contact hole C2. After deposition of a thin copper film PM2 b as a seed film for electroplating, a copper film PM2 c is formed over the copper film PM2 b by electroplating. In a reducing atmosphere, the substrate 1 is annealed (heat treated), followed by removal of the copper films PM2 c and PM2 b and barrier film PM2 a outside the wiring trench HM2 and contact hole C2 by CMP or etchback, whereby the second-level interconnect M2 and a plug (connecting portion) P2 for connecting the first-level interconnect M1 with the second-level interconnect, each made of the copper films PM2 b, PM2 c and barrier film PM2 a, are formed.

[0246] As in Embodiment 1, selective growth or preferential growth of tungsten (W) is effected over the second-level interconnect M2, whereby a tungsten film CM2 is formed.

[0247] As illustrated in FIG. 25, a TEOS film 28 a, an SiOC film 28 b and another TEOS film 28 c are then deposited successively, as an insulating film, by CVD over the low dielectric constant insulating film 26 b and tungsten film CM2. These films are similarly formed to the TEOS films 24 a and 24 c, and the SiOC film 24 b. Over the TEOS film 28 c, a low dielectric constant insulating film 30 b is formed as an insulating film by using a coating material such as aromatic polymer material. This film is similarly formed to the low dielectric constant insulating film 22 b.

[0248] In the above-described four-layer insulating film, a wiring trench and a contact hole are formed in a similar manner to that employed for the formation of the wiring trench HM2 and contact hole C2, but illustration of this step is omitted.

[0249] According to this Embodiment, the wiring trench HM2 and contact hole C2 are formed in the four-layer insulating film (24 a, 24 b, 24 c, 26 b) so that their formation step can be simplified compared with that in Embodiment 1. The insulating film in which the first-level interconnect is to be formed may be constituted of the TEOS film 22 a and low dielectric constant insulating film 22 b and the TEOS film 22 c as shown in Embodiment 1 may be omitted. FIG. 25 illustrates the case in which 22 c is omitted.

[0250] Since the tungsten film CM1 an barrier film PM2 a between the first-level interconnect M1 and plug P2 are removed, contact resistance between the first-level interconnect M1 and plug P2 can be reduced and electromigration resistance can be improved. Thus, similar effects as described in Embodiment 1 are available.

[0251] (Embodiment 3)

[0252] In Embodiment 1, the wiring trench HM2 to embed the second-level interconnect M2 therein was formed in the insulating film 26 and TEOS film 24 c. This wiring trench HM2 may be formed in the insulating film 26. FIG. 26 is a fragmentary cross-sectional view of a substrate illustrating the manufacturing method of a semiconductor device according to Embodiment 3 of the present invention.

[0253] The semiconductor device of this embodiment of the present invention will next be described in accordance with its manufacturing method. Steps up to the formation of the first-level interconnect M1 and the tungsten film CM1 thereover are similar to those described above in Embodiment 1 with reference to FIGS. 1 to 6, so that their description is omitted.

[0254] As illustrated in FIG. 26, a TEOS film 24 a, an SiOC film 24 b and another TEOS film 24 c are successively deposited by CVD as an insulating film over the TEOS film 22 c and tungsten film CM1. Then, over the TEOS film 24 c, a low dielectric constant insulating film 26 b, using an aromatic polymer material, and a TEOS film 26 c are successively formed as an insulating film. The properties or shape of these five films (24 a, 24 b, 24 c, 26 b, 26 c) are as described in detail in Embodiment 1.

[0255] In the TEOS films 24 a and 24 c, and SiOC film 24 b of these five films (24 a, 24 b, 24 c, 26 b, 26 c), a contact hole C2 for the formation of a plug (connecting portion) P2 for connecting the first-level interconnect M1 and the second-level interconnect M2 is formed, while in the low dielectric constant insulating film 26 b and TEOS film 26 c, a wiring trench HM2 is formed.

[0256] As in Embodiment 1, a hard mask (not illustrated) having an opening in a second-level interconnect formation region is formed over the TEOS film 26 c, followed by the formation, over the hard mask, of a resist film (not illustrated) having an opening in a connecting region of the first-level interconnect and the second-level interconnect.

[0257] With the resist film as a mask, the insulating film 26 (26 b, 26 c), TEOS film 24 c and SiOC film 24 b are removed to form the contact hole C2, followed by the removal of the resist film. With the hard mask as a mask, the insulating film 26 (26 b, 26 c) is removed to form the wiring trench HM2 and the TEOS film 24 a is removed from the bottom of the contact hole C2. The contact hole C2 may be formed after the formation of the wiring trench HM2.

[0258] The tungsten film CM1 exposed from the bottom of the contact hole C2 is removed, for example, by dry etching to expose the copper film M1 c.

[0259] Steps on and after the formation of the second-level interconnect M2 and plug (connecting portion) P2 are similar to those of Embodiment 1 so that only their outline will next be described.

[0260] As in Embodiment 1, a barrier film PM2 a is formed over the TEOS film 26 c including the insides of the wiring trench HM2 and contact hole C2. It is deposited to give a thickness of about 5 nm on the side walls of the wiring trench HM2, about 30 nm on the bottom of the wiring trench HM2, about 3 nm on the side walls of the contact hole C2 and about 20 nm on the bottom of the contact hole C2.

[0261] As in Embodiment 1, the barrier film PM2 a is removed from the bottom of the contact hole C2. After deposition of a thin copper film PM2 b as a seed film for electroplating, a copper film PM2 c is formed over the copper film PM2 b by electroplating. In a reducing atmosphere, the substrate 1 is annealed (heat treated), followed by removal of the copper films PM2 c and PM2 b and barrier film PM2 a outside the wiring trench HM2 and contact hole C2 by CMP or etchback, whereby a second-level interconnect M2 and a plug (connecting portion) P2 for connecting the first-level interconnect M1 with the second-level interconnect, each made of the copper films PM2 b, PM2 c and barrier film PM2 a, are formed.

[0262] As in Embodiment 1, selective growth or preferential growth of tungsten (W) is effected over the second-level interconnect M2, whereby a tungsten film CM2 is formed.

[0263] As illustrated in FIG. 26, a TEOS film 28 a, an SIOC film 28 b and another TEOS film 28 c are then deposited successively, as an insulating film, by CVD over the TEOS film 26 c and tungsten film CM2. These films are similarly formed to the SiOC film 24 b, and the TEOS films 24 a and 24 c. Over the TEOS film 28 c, a low dielectric constant insulating film 30 b, using an aromatic polymer material, and a TEOS film (not illustrated) are formed successively as an insulating film. These films are similarly formed to the low dielectric constant insulating film 22 b and the TEOS film 22 c.

[0264] In the above-described five-layer insulating film, a wiring trench and a contact hole are formed in a similar manner to that employed for the formation of the wiring trench HM2 and contact hole C2, but illustration of this step is omitted.

[0265] The wiring trench HM2 can thus be formed in the insulating film (26).

[0266] Also in this Embodiment, since the tungsten film CM1 an barrier film PM2 a between the first-level interconnect M1 and plug P2 are removed, contact resistance between the first-level interconnect M1 and plug P2 can be reduced and electromigration resistance can be improved. Thus, similar effects as described in Embodiment 1 are available.

[0267] (Embodiment 4)

[0268] In Embodiment 2, diffusion of copper, which constitutes an interconnect, into an insulating film and formation of an oxide due to the contact between a silicon oxide film and a copper film were prevented by forming tungsten films CM1, CM2 over interconnects M1, M2. The prevention of copper diffusion or oxidation may be reinforced by forming a thin silicon nitride film over these tungsten films. FIG. 27 is a fragmentary cross-sectional view of a substrate illustrating the manufacturing method of a semiconductor device according to Embodiment 4 of the present invention.

[0269] The semiconductor device of this embodiment of the present invention will next be described in accordance with its manufacturing method. Steps up to the formation of the first-level interconnect M1 and the tungsten film CM1 thereover are similar to those described above in Embodiment 1 with reference to FIGS. 1 to 6, so that their description is omitted.

[0270] As illustrated in FIG. 27, a silicon nitride film 401 is deposited by CVD as a copper diffusion preventive film or an antioxidant film. This silicon nitride film is formed to have a thickness of 20 nm or less, because as described specifically in Embodiment 1, an effective dielectric constant of an insulating film existing between interconnects is reduced by thinning, as much as possible, the silicon nitride film having a large dielectric constant.

[0271] Then, over the silicon nitride film 401, an SiOC film 24 b and a TEOS film 24 c are successively deposited as an insulating film by CVD. Over the TEOS film 24 c, a low dielectric constant insulating film 26 b, using an aromatic polymer material, and another TEOS film 26 c are successively formed as an insulating film. The properties or shape of these four films (24 b, 24 c, 26 b, 26 c) are as described in detail in Embodiment 1.

[0272] In the SiOC film 24 b of these four films (24 b, 24 c, 26 b, 26 c) and the silicon nitride film 401, a contact hole C2 for the formation of a plug (connecting portion) P2 for connecting the first-level interconnect M1 and the second-level interconnect M2 is formed, while in the TEOS film 24 c, the low dielectric constant insulating film 26 b, and the TEOS film 26 c, a wiring trench HM2 is formed.

[0273] As in Embodiment 1, a hard mask (not illustrated) having an opening in a second-level interconnect formation region is formed over the TEOS 26 c, followed by the formation of a resist film (not illustrated) having an opening in a connecting region of the first-level interconnect and the second-level interconnect.

[0274] With the resist film as a mask, the TEOS film 24 c and SiOC film 24 b, among the insulating film 26 and insulating film 24, are removed to form the contact hole C2. After removal of the resist film, the insulating film 26 (26 b, 26 c) and TEOS film 24 c are removed with the hard mask as a mask to form the wiring trench HM2. The contact hole C2 may be formed after the formation of the wiring trench HM2.

[0275] The silicon nitride film 401 exposed from the bottom of the contact hole C2 and the underlying tungsten film CM1 are removed, for example, by dry etching to expose a copper film M1 c.

[0276] Steps on and after the formation of the second-level interconnect M2 and plug (connecting portion) P2 are similar to those of Embodiment 1 so that only their outline will next be described.

[0277] As in Embodiment 1, a barrier film PM2 a is formed over the TEOS film 26 c including the insides of the wiring trench HM2 and contact hole C2. It is deposited to give a thickness of about 5 nm on the side walls of the wiring trench HM2, about 30 nm on the bottom of the wiring trench HM2, about 3 nm on the side walls of the contact hole C2 and about 20 nm on the bottom of the contact hole C2.

[0278] As in Embodiment 1, the barrier film PM2 a is removed from the bottom of the contact hole C2. After deposition of a thin copper film PM2 b as a seed film for electroplating, a copper film PM2 c is formed over the copper film PM2 b by electroplating. In a reducing atmosphere, the substrate 1 is annealed (heat treated), followed by removal of the copper films PM2 c and PM2 b and barrier film PM2 a outside the wiring trench HM2 and contact hole C2 by CMP or etchback, whereby a second-level interconnect M2 and a plug (connecting portion) P2 for connecting the first-level interconnect M1 with the second-level interconnect, each made of the copper films PM2 b, PM2 c and barrier film PM2 a, are formed.

[0279] As in Embodiment 1, selective growth or preferential growth of tungsten (W) is effected over the second-level interconnect M2, whereby a tungsten film CM2 is formed. Over the tungsten film CM2, then, a silicon nitride film 402 is deposited by CVD as a copper diffusion preventive film or an antioxidant film. This silicon nitride film is formed to have a thickness of 20 nm or less.

[0280] As illustrated in FIG. 27, an SiOC film 28 b and a TEOS film 28 c are then deposited successively, as an insulating film, by CVD over the silicon nitride film 402. These films are similarly formed to the SiOC film 24 b and TEOS film 24 c. Over the TEOS film 28 c, a low dielectric constant insulating film 30 b, using an aromatic polymer material, and a TEOS film (not illustrated) are formed successively as an insulating film. These films are similarly formed to the low dielectric constant insulating film 22 b and TEOS film 22 c.

[0281] In these insulating films, a wiring trench and a contact hole are formed in a similar manner to that employed for the formation of the wiring trench HM2 and contact hole C2, but illustration of this step is omitted.

[0282] According to this Embodiment, prevention of copper diffusion or oxidation can be reinforced, because thin silicon nitride films 401, 402 are formed over the tungsten films CM1, CM2. By adjusting the thickness of these silicon nitride films 401, 402 to 20 nm or less, the effective dielectric constant of the insulating film existing between interconnects can be reduced.

[0283] Since the tungsten film CM1 an barrier film PM2 a between the first-level interconnect M1 and plug P2 are removed, contact resistance between the first-level interconnect M1 and plug P2 can be reduced and electromigration resistance can be improved. Thus, similar effects as described in Embodiment 1 are available.

[0284] (Embodiment 5)

[0285] In Embodiment 1, the uppermost insulating film filled with the interconnects M1, M2 were TEOS films 22 c, 26 c, which may be substituted with a silicon nitride film. Alternatively, a TMS film, SiC film or SiCN film which is a barrier insulating film having a lower dielectric constant than that of a silicon nitride film may be employed. Such a low dielectric constant insulating film can be formed by CVD, for example, by using trimethoxysilane and dinitrogen monoxide (N₂O). This film is composed mainly of SiON (this film will hereinafter be called “TMS film”). Alternatively, an SiC film may be formed using trimethylsilane, or an SiCN film may be formed using trimethylsilane and ammonia.

[0286] In short, the TEOS films 22 c, 26 c in Embodiment 1 are substituted in Embodiment 5 with barrier insulating films 501, 502 such as a silicon nitride film, SiO film, TMS film, SiC film or SiCN film.

[0287]FIG. 28 is a fragmentary cross-sectional view of a substrate for illustrating the manufacturing method of a semiconductor device according to Embodiment 5 of the present invention.

[0288] The semiconductor device of this embodiment of the present invention will next be described in accordance with its manufacturing method. Steps up to the formation of a silicon oxide film 20 and a plug PI embedded in this film are similar to those described above in Embodiment 1 with reference to FIG. 1, so that their description is omitted.

[0289] As illustrated in FIG. 28, a TEOS film 22 a is formed as an insulating film over the silicon oxide film 20 and plug 1 as in Embodiment 1. Then, a low dielectric constant insulating film 22 b is formed by application to the TEOS film 22 a, followed by heat treatment. This low dielectric constant insulating film may be formed by CVD, instead.

[0290] Over the low dielectric constant insulating film 22 b, a barrier insulating film 501 such as silicon nitride film, SiON film, TMS film, SiC film or SiCN film is formed as a copper diffusion preventive film or an antioxidant film.

[0291] The low dielectric constant insulating film 22 b is sandwiched by the films (22 a, 501) formed by CVD in order to maintain the mechanical strength of the laminate film of them. In the three-layer insulating film (22) composed of TEOS film 22 a, low dielectric constant insulating film 22 b and barrier insulating film 501 such as silicon nitride film, a wiring trench HM1 is formed.

[0292] The insulating film 22 (22 a, 22 b, 501) in which a first-level interconnect is to be formed is removed by photolithography and dry etching, whereby a wiring trench HM1 is formed. This wiring trench HM1 has a thickness of about 0.25 μm and a width of 0.18 μm.

[0293] Over the insulating film 22 including the inside of the wiring trench HM1, a barrier film M1 a is deposited, for example, by sputtering as in Embodiment 1, followed by the formation of a thin copper film M1 b, as a seed film for electroplating, over the barrier film M1 a by ionized sputtering. A copper film M1 c is then formed over the copper M1 b, for example, by electroplating. This copper film M1 c is formed so to embed in the wiring trench HM1.

[0294] In a reducing atmosphere, the substrate 1 is annealed (heat treated), followed by removal of the copper films M1 c and M1 b and barrier film M1 a outside the wiring trench HM1 by CMP or etchback, whereby a first-level interconnect M1 composed of the copper films M1 c, M1 b and barrier film M1 a is formed. At this time, in a region outside a first-level interconnect M1 formation region, the barrier film 501 such as silicon nitride film, SiON film, TMS film, SiC film, SiOC film, SiOCN film, or SiCN film is exposed. Then, in a reducing atmosphere, the substrate 1 is annealed (heat treated).

[0295] As in Embodiment 1, selective growth or preferential growth of tungsten (W) as a capping conductive film is effected over the first-level interconnect M1, whereby a tungsten film CM1 of about 2 to 20 nm is formed over the first-level interconnect M1. Prior to the formation of the tungsten film CM1, washing or hydrogen treatment may be conducted. Alternatively, washing may be conducted after the formation of the tungsten film CM1.

[0296] Over the barrier insulating film 501 such as silicon nitride film, SiON film, TMS film, SiC film, SiOC film, SiOCN film, or SiCN film and the tungsten film CM1, a TEOS film 24 a, an SiOC film 24 b and another TEOS film 24 c are successively deposited by CVD as an insulating film. Then, a low dielectric constant insulating film 26 b using an aromatic polymer material is formed as an insulating film over the TEOS film 24 c, followed by the formation of a barrier insulating film 502 such as a silicon nitride film, SiON film, TMS film, SiC film, SiOC film, SiOCN film, or SiCN film in a similar manner to that employed for the formation of the barrier insulating film 501 such as silicon nitride film, SiON film, TMS film, SiC film, SiOC film, SiOCN film, or SiCN film. The properties and shapes of these films 24 a, 24 b, 24 c and 26 b are as described in detail in Embodiment 1.

[0297] In the TEOS film 24 a and SiOC film 24 b of these five films (24 a, 24 b, 24 c, 26 b, 502), a contact hole C2 for the formation of a plug (connecting portion) P2 for connecting the first-level interconnect M1 with the second-level interconnect M2 is formed, while in the TEOS film 24 c, low dielectric constant insulating film 26 b and silicon nitride film 502, a wiring trench HM2 is formed.

[0298] As in Embodiment 1, a hard mask (not illustrated) having an opening in a second-level interconnect formation region is formed over the barrier insulating film 502, followed by the formation of a resist film (not illustrated) having an opening in a connecting region of the first-level interconnect with the second-level interconnect.

[0299] With the resist film as a mask, the insulating film 26 (502, 26 b), TEOS film 24 c and SiOC film 24 b are removed to form the contact hole C2, followed by the removal of the resist film. With the hard mask as a mask, the insulating film 26 (502 and 26 b) and TEOS film 24 c are removed to form the wiring trench HM2 and the TEOS film 24 a is removed from the bottom of the contact hole C2. The contact hole C2 may be formed after the formation of the wiring trench HM2.

[0300] The tungsten film CM1 exposed from the bottom of the contact hole C2 is then removed, for example, by dry etching to expose a copper film M1 c.

[0301] Steps on and after the formation of the second-level interconnect M2 and plug (connecting portion) P2 are similar to those in Embodiment 1 so that only their outline will next be described.

[0302] As in Embodiment 1, a barrier film PM2 a is formed over the barrier film 502 such as silicon nitride film, SiON film, TMS film, SiC film, SiOC film, SiOCN film, or SiCN film including the insides of the wiring trench HM2 and contact hole C2. It is deposited to give a thickness of about 5 nm on the side walls of the wiring trench HM2, about 30 nm on the bottom of the wiring trench HM2, about 3 nm on the side walls of the contact hole C2 and about 20 nm on the bottom of the contact hole C2.

[0303] As in Embodiment 1, the barrier film PM2 a is removed from the bottom of the contact hole C2. After deposition of a thin copper film PM2 b as a seed film for electroplating, a copper film PM2 c is formed over the copper film PM2 b by electroplating. In a reducing atmosphere, the substrate 1 is annealed (heat treated), followed by removal of the copper films PM2 c and PM2 b and barrier film PM2 a outside the wiring trench HM2 and contact hole C2 by CMP or etchback, whereby a second-level interconnect M2 and a plug (connecting portion) P2 for connecting the first-level interconnect M1 with the second-level interconnect, each made of the copper films PM2 b, PM2 c and barrier film PM2 a, are formed.

[0304] As in Embodiment 1, selective growth or preferential growth of tungsten (W) is effected over the second-level interconnect M2, whereby a tungsten film CM2 is formed.

[0305] As illustrated in FIG. 28, a TEOS film 28 a, an SiOC film 28 b and a TEOS film 28 c are then deposited successively, as an insulating film, by CVD over the barrier insulating film 502 and tungsten film CM2. These films are similarly formed to the SiOC film 24 b and TEOS films 24 a, 24 c. Over the TEOS film 28 c, a low dielectric constant insulating film 30 b using an aromatic polymer material and a silicon nitride film, SiON film, TMS film, SiC film, SiOC film, SiOCN film, or SiCN film (not illustrated) are successively formed as an insulating film. These films are similarly formed to the low dielectric constant insulating film 22 b or the barrier insulating film 502 such as silicon nitride film, SiON film, TMS film, SiC film, SiOC film, SiOCN film or SiCN film.

[0306] In the above-described five-layer insulating film, a wiring trench and a contact hole are formed in a similar manner to that employed for the formation of the wiring trench HM2 and contact hole C2, but illustration of this step is omitted.

[0307] In this Embodiment, the barrier insulating films 501, 502 such as silicon nitride film, SiON film, TMS film, SiC film, SiOC film, SiOCN film and SiCN film are employed as the uppermost insulating film in which the interconnects M1, M2 are to be embedded. So, even if mask misalignment occurs upon formation of the contact hole C2 and the pattern of the contact hole C2 (plug P2) invades the first-level interconnect M1 and reaches even to the silicon nitride film 501, this barrier insulating film 501 prevents diffusion of copper from the copper film constituting the plug P2 and moreover, oxidation of the copper film due to the contact between the copper film and silicon oxide film (low dielectric constant insulating film 22 b) can be prevented. The barrier insulating film having a thickness as thin as possible is preferred in order to reduce the effective dielectric constant of the insulating film existing between the interconnects.

[0308] When the interconnect width of the first-level interconnect M1 and the diameter of the contact hole C2 are designed to be equal for the purpose of heightening the density and integration degree of interconnects as illustrated in FIG. 28, misalignment of a mask due to margin latitude occurs between the first-level interconnect M1 and contact hole C2. Even if such a misalignment occurs, the barrier insulating film 501 formed on the bottom of the contact hole C2 can prevent diffusion of copper from the copper film constituting the plug P2 toward the insulating film 22 b via the bottom of the contact hole C2.

[0309] Even if misalignment occurs as described above, the barrier properties against copper diffusion can thus be maintained on the bottom of the contact hole C2 so that the interconnect width of the first-level interconnect M1 and the diameter of the contact hole C2 can be designed to be equal and density and integration degree of interconnects can be heightened without losing the reliability of the interconnect.

[0310] Since the tungsten film CM1 and barrier film PM2 a between the first-level interconnect M1 and plug P2 are removed, effects as described in Embodiment 1 such as a reduction in the contact resistance between the first-level interconnect M1 and plug P2 and improvement in electromigration resistance are available.

[0311] (Embodiment 6)

[0312] In Embodiment 1, after removal of the barrier film PM2 a from the bottom of the contact hole C2, copper films PM2 b, PM2 c were formed. The barrier film PM2 a may be left between the second-level interconnect M2 and plug P2 without removing it from the bottom of the contact hole C2. FIGS. 29 and 30 are fragmentary cross-sectional views of a substrate for illustrating the manufacturing method of a semiconductor device according to Embodiment 6 of the present invention.

[0313] The semiconductor device of this embodiment of the present invention will next be described in accordance with its manufacturing method. Steps up to the formation of the first-level interconnect M1 and the tungsten film CM1 thereover are similar to those described above in Embodiment 1 with reference to FIGS. 1 to 6, so that their description is omitted. In FIG. 29, the plug P1 in the silicon oxide film 20 is omitted (which will equally apply to FIGS. 30 to 32).

[0314] As illustrated in FIG. 29, a TEOS film 24 a, an SiOC film 24 b and another TEOS film 24 c are successively deposited by CVD as an insulating film over the substrate 1 (tungsten film CM1). Then, over the TEOS film 24 c, a low dielectric constant insulating film 26 b using an aromatic polymer material and a TEOS film 26 c are successively formed as an insulating film. The properties or shape of these five films (24 a, 24 b, 24 c, 26 b, 26 c) are as described in detail in Embodiment 1.

[0315] In the SiOC film 24 b and TEOS film 24 a of these five films (24 a, 24 b, 24 c, 26 b, 26 c), a contact hole C2 for the formation of a plug (connecting portion) P2 for connecting the first-level interconnect M1 with the second-level interconnect M2 is formed, while in the TEOS films 24 c and 26 c, and the low dielectric constant insulating film 26 b, a trench HM2 is formed.

[0316] As in Embodiment 1, a hard mask (similar to that illustrated in FIG. 9) having an opening in a second-level interconnect formation region is formed over the TEOS film 26 c, followed by the formation, over the hard mask, of a resist film (similar to that in FIG. 10) having an opening in a connecting region of the first-level interconnect and the second-level interconnect.

[0317] With the resist film as a mask, the TEOS films 24 c and 24 a, and SiOC film 24 b, among the TEOS film 26 c, low dielectric constant insulating film 26 b and insulating film 24, are removed to form the contact hole C2 (similar to that in FIG. 10). After removal of the resist film, the TEOS films 26 c and 24 c and low dielectric constant insulating film 26 b are removed with the hard mask as a mask to form the wiring trench HM2 (similar to that in FIG. 11). The contact hole C2 may be formed after the formation of the wiring trench HM2.

[0318] The tungsten film CM1 exposed from the bottom of the contact hole C2 is removed, for example, by dry etching to expose a copper film M1 c (similar to that in FIG. 12). The tungsten film CM1 may be removed completely, or a discontinuous tungsten film may be left on the bottom of the contact hole.

[0319] As in Embodiment 1, a barrier film PM2 a is formed over the TEOS film 26 c including the insides of the wiring trench HM2 and contact hole C2. It is deposited to give a thickness of about 5 nm on the side walls of the wiring trench HM2, about 30 nm on the bottom of the wiring trench HM2, about 3 nm on the side walls of the contact hole C2 and about 20 nm on the bottom of the contact hole C2.

[0320] As in Embodiment 1, after deposition of a thin copper film PM2 b over the barrier film PM2 a as a seed film for electroplating, a copper film PM2 c is formed over the copper film PM2 b by electroplating. In a reducing atmosphere, the substrate 1 is annealed (heat treated), followed by removal of the copper films PM2 c and PM2 b and barrier film PM2 a outside the wiring trench HM2 and contact hole C2 by CMP or etchback, whereby a second-level interconnect M2 and a plug (connecting portion) P2 for connecting the first-level interconnect M1 with the second-level interconnect, each made of the copper films PM2 b, PM2 c and barrier film PM2 a, are formed.

[0321] As in Embodiment 1, selective growth or preferential growth of tungsten (W) is effected over the second-level interconnect M2, whereby a tungsten film CM2 is formed.

[0322] As illustrated in FIG. 29, an insulating film such as TEOS film 28 a is then deposited over the TEOS film 26 c and tungsten film CM2.

[0323] On the bottom of the contact hole C2 which is a joint portion of the first-level interconnect M1 and plug (connecting portion) P2, the barrier film PM2 a is not removed from the bottom of the contact hole C2. This means that the number of the fabrication steps can be reduced compared with those of Embodiment 1, because only the tungsten film CM1 must be removed from the bottom of the contact hole C2 and the removing step of the barrier film PM2 a from the bottom of the contact hole C2 can be omitted.

[0324] In this Embodiment, the tungsten film CM1 between the first-level interconnect M1 and plug P2 is removed so that contact resistance therebetween can be reduced. The reducing effect may be a little small because the barrier film PM2 a exists between the first-level interconnect M1 and plug P2, but effects as described in Embodiment 1 such as improvement in electromigration resistance are available. The copper film PM2 b may be deposited after the barrier film PM2 a is thinned by etching of the surface thereof.

[0325] In FIG. 37, described is an example of application of this Embodiment 6 to a case in which the interconnect width of the first-level interconnect M1 and the diameter of the contact hole C2 are designed to be equal for the purpose of heightening of density and integration degree of interconnects. As illustrated in FIG. 37, when the interconnect width of the first-level interconnect M1 and the diameter of the contact hole C2 are designed to be equal, a mask misalignment occurs upon formation of the contact hole C2 and the pattern of the contact hole C2 is formed to invade the first-level interconnect M1 and extend even to the low dielectric constant insulating film 22 c. Even in such a case, diffusion of copper from the copper film constituting the plug P2 toward the insulating film 22 c can be prevented on the bottom of the contact hole C2, because the barrier film PM2 a is formed on the side walls and bottom of the contact hole C2. Moreover, oxidation of the copper film due to the contact between the copper film and silicon oxide film (TEOS film 22 c) can be prevented.

[0326] Even if misalignment occurs, the barrier properties against copper diffusion can thus be maintained on the bottom of the contact hole C2 so that the interconnect width of the first-level interconnect M1 and the diameter of the contact hole C2 can be designed to be equal and density and integration degree of the interconnects can be heightened without losing the reliability of the interconnect. In addition, a step of removing the barrier film PM2 a from the bottom of the contact hole C2 can be omitted so that the number of fabrication steps can be reduced compared with that of Embodiment 1.

[0327] As illustrated in FIG. 30, the barrier film PM2 a between the first-level interconnect M1 and plug P2 may be formed as a discontinuous film.

[0328] In such a case, the barrier film PM2 a is not formed uniformly all over the bottom of the contact hole C2, but is partially formed. It is a discontinuous film which permits direct contact of the copper films M1 c, M1 b with the copper films PM2 b, PM2 c at portions in which the barrier film PM2 a is not formed.

[0329] On the bottom of the contact hole C2 which is a joint between the first-level interconnect M1 and plug (connecting portion) P2, a barrier material for preventing copper diffusion is formed as a discontinuous film.

[0330] Such a discontinuous film can be formed, for example, by forming the barrier film PM2 a over the TEOS film 26 c including the insides of the wiring trench HM2 and contact hole C2, while controlling the film forming conditions so as to make the barrier film markedly thin on the bottom of the contact hole C2.

[0331] Alternatively, such a discontinuous film can be formed in the following manner. After deposition, over the TEOS film 26 c including the insides of the wiring trench HM2 and contact hole C2, of the barrier film PM2 a to a thickness of about 5 nm on the side walls of the wiring trench HM2, about 30 nm on the bottom of the wiring trench HM2, about 3 nm on the side walls of the contact hole C2 and about 20 nm on the bottom of the contact hole C2, the barrier film PM2 a is removed from the bottom of the contact hole C2. Upon removal, etching conditions are controlled so as not to completely remove the barrier film.

[0332] As described above, if the barrier film PM2 a existing between the first-level interconnect M1 and plug P2 is formed as a discontinuous film, contact resistance therebetween can be reduced. In addition, it enables transfer of copper via the discontinuous portion of the barrier film PM2 a, whereby effects such as improvement in the electromigration resistance as described in Embodiment 1 are available.

[0333] (Embodiment 7)

[0334] In Embodiment 1, the copper films PM2 b, PM2 c were formed after removal of the tungsten film CM1 from the bottom of the contact hole C2. Alternatively, the tungsten film CM1 may be left between the second-level interconnect M2 and plug P2 without removing it from the bottom of the contact hole C2. FIG. 31 is a fragmentary cross-sectional view of a substrate for illustrating the manufacturing method of a semiconductor device according to Embodiment 7 of the present invention.

[0335] The semiconductor device of this Embodiment of the present invention will next be described in accordance with its manufacturing method. The steps up to the formation of the first-level interconnect M1 and the tungsten film CM1 thereover are similar to those of Embodiment 1 which were described with reference to FIGS. 1 to 6 so that the description of them are omitted.

[0336] Then, as illustrated in FIG. 31, insulating films such as a TEOS film 24 a, an SiOC film 24 b and another TEOS film 24 c are deposited successively over the substrate 1 (tungsten film CM1) by CVD. Over the TEOS film 24 c, a low dielectric constant insulating film 26 b using an aromatic polymer material and a TEOS film 26 c are successively formed as an insulating film. The properties and shape of these five films (24 a, 24 b, 24 c, 26 b, 26 c) are as described in detail in Embodiment 1.

[0337] In the SiOC film 24 b and TEOS film 24 a, of these five films (24 a, 24 b, 24 c, 26 b, 26 c), a contact hole C2 for the formation of a plug (connecting portion) P2 for connecting the first-level interconnect M1 with the second-level interconnect M2 is formed, while in the TEOS films 24 c and 26 c, and low dielectric constant insulating film 26 b, a wiring trench HM2 is formed.

[0338] As in Embodiment 1, a hard mask (similar to that of FIG. 9) having an opening in a second-level interconnect formation region is formed over the TEOS film 26 c, followed by the formation of a resist film (similar to that of FIG. 10) having an opening in a connecting region of the first-level interconnect and the second-level interconnect.

[0339] With the resist film as a mask, the TEOS film 26 c, low dielectric constant insulating film 26 b, TEOS films 24 c and 24 a, and SiOC film 24 b are removed to form the contact hole C2 (similar to that of FIG. 10). After removal of the resist film, the TEOS films 26 c and 24 c, and low dielectric constant insulating film 26 b are removed with the hard mask as a mask to form the wiring trench HM2. The contact hole C2 may be formed after the formation of the wiring trench HM2 (similar to that of FIG. 11). The hard mask MK is then removed. The second-level interconnect M2 and plug (connecting portion) P2 will next be formed while the tungsten film CM1 is exposed from the bottom of the contact hole C2. Steps on and after the formation of the second-level interconnect M2 and plug P2 are similar to those in Embodiment 1 so that only their outline will next be described.

[0340] As in Embodiment 1, a barrier film PM2 a is formed over the TEOS film 26 c including the insides of the wiring trench HM2 and contact hole C2 from which the tungsten film CM1 is exposed. It is deposited to give a thickness of about 5 nm on the side walls of the wiring trench HM2, about 30 nm on the bottom of the wiring trench HM2, about 3 nm on the side walls of the contact hole C2 and about 20 nm on the bottom of the contact hole C2.

[0341] As in Embodiment 1, the barrier film PM2 a is removed from the bottom of the contact hole C2. After deposition of a thin copper film PM2 b as a seed film for electroplating, a copper film PM2 c is formed over the copper film PM2 b by electroplating. In a reducing atmosphere, the substrate 1 is annealed (heat treated), followed by removal of the copper films PM2 c and PM2 b and barrier film PM2 a outside the wiring trench HM2 and contact hole C2 by CMP or etchback, whereby a second-level interconnect M2 and a plug (connecting portion) P2 for connecting the first-level interconnect M1 with the second-level interconnect, each made of the copper films PM2 b, PM2 c and barrier film PM2 a, are formed.

[0342] As in Embodiment 1, selective growth or preferential growth of tungsten (W) is effected over the second-level interconnect M2, whereby a tungsten film CM2 is formed.

[0343] Over the TEOS film 26 c and tungsten film CM2, a TEOS film 28 a is then deposited as an insulating film as illustrated in FIG. 31.

[0344] In this Embodiment, the barrier film PM2 a between the first-level interconnect M1 and plug P2 is removed so that contact resistance therebetween can be reduced. The reducing effect may be a little small because the tungsten film CM1 exists between the first-level interconnect M1 and plug P2, but effects as described in Embodiment 1 such as improvement in electromigration resistance are available.

[0345] On the bottom of the contact hole C2 which is a joint portion of the first-level interconnect M1 and plug (connecting portion) P2, the tungsten film CM1 exists but the barrier film PM2 a is not formed on the bottom of the contact hole C2. This means that the number of the fabrication steps can be reduced compared with those of Embodiment 1, because only the barrier film PM2 a must be removed from the bottom of the contact hole C2 and the removing step of the tungsten film CM1 from the bottom of the contact hole C2 can be omitted.

[0346] In FIG. 38, described is an example of application of this Embodiment 7 to a case in which the interconnect width of the first-level interconnect M1 and the diameter of the contact hole C2 are designed to be equal for the purpose of heightening of density and integration degree of interconnects. As illustrated in FIG. 38, an insulating film 22 has a constitution similar to that of Embodiment 5. Described specifically, as illustrated in FIG. 38, after formation of an insulating film such as TEOS film 22 a as in Embodiment 5 over the silicon oxide film 20 and plug P1, a low dielectric constant insulating film 22 b is formed by application onto the TEOS film 22 a, followed by heat treatment. Alternatively, the low dielectric constant insulating film may be formed by CVD.

[0347] Then, over the low dielectric constant insulating film 22 b, a barrier insulating film 501 such as silicon nitride film, SiON film, TMS film, SiC film or SiCN film is formed by CVD as a copper diffusion preventive film or anti-oxidant film.

[0348] Steps on and after the above-described step are similar to those of Embodiment 7 described above with reference to FIG. 31 so that description on them is omitted.

[0349] In this Embodiment, the barrier insulating film 501 is employed as the uppermost insulating film in which the interconnect M1 is to be embedded. So, even if mask misalignment occurs upon formation of the contact hole C2 and the pattern of the contact hole C2 invades the first-level interconnect M1 and reaches even the barrier insulating film 501, this barrier insulating film 501 on the bottom of the contact hole C2 can prevent diffusion of copper from the copper film constituting the plug P2 toward the insulating film 22 b and moreover, can prevent oxidation of the copper film due to the contact between the copper film and silicon oxide film (low dielectric constant insulating film 22 b). The barrier insulating film having a thickness as thin as possible is preferred in order to reduce the effective dielectric constant of the insulating film existing between the interconnects.

[0350] Even if misalignment occurs, the barrier properties against copper diffusion can thus be maintained on the bottom of the contact hole C2 so that the interconnect width of the first-level interconnect M1 and the diameter of the contact hole C2 can be designed to be equal and density and integration degree of interconnects can be heightened without losing the reliability of them. In addition, a step of removing the tungsten film CM1 from the bottom of the contact hole C2 can be omitted so that the number of fabrication steps can be reduced compared with that of Embodiment 1.

[0351] (Embodiment 8)

[0352] In Embodiment 1, single-layer tungsten films CM1, CM2 are formed over the interconnects M1, M2 as the capping conductive film. This capping conductive film may be substituted with a laminate film. FIG. 32 is a fragmentary cross-sectional view of a substrate for illustrating the manufacturing method of a semiconductor device according to Embodiment 8 of the present invention.

[0353] The semiconductor device of this Embodiment of the present invention will next be described in accordance with its manufacturing method. Steps up to the formation of the first-level interconnect M1 and the tungsten film CM1 thereover are similar to those described above in Embodiment 1 with reference to FIGS. 1 to 6, so that their description is omitted.

[0354] Then, as illustrated in FIG. 32, the tungsten film CM1 is converted into a tungsten nitride film CM1 a by treatment in a nitrogen atmosphere, followed by selective growth or preferential growth of tungsten (W) over the tungsten nitride film CM1 a as in Embodiment 1, whereby a tungsten film CM1 b is formed. The resulting tungsten nitride film CM1 a and tungsten film CM1 b constitute a capping conductive film 801.

[0355] Over the substrate (tungsten film CM1 b), a TEOS film 24 a, an SiOC film 24 b and another TEOS film 24 c are successively deposited by CVD as an insulating film. Then, over the TEOS film 24 c, a low dielectric constant insulating film 26 b using an aromatic polymer material and a TEOS film 26 c are successively formed as an insulating film. The properties or shape of these five films (24 a, 24 b, 24 c, 26 b, 26 c) are as described in detail in Embodiment 1.

[0356] In the SiOC film 24 b and TEOS film 24 a, among these five films (24 a, 24 b, 24 c, 26 b, 26 c), a contact hole C2 for the formation of a plug (connecting portion) P2 for connecting the first-level interconnect M1 with the second-level interconnect M2 is formed, while in the TEOS films 24 c and 26 c, and the low dielectric constant insulating film 26 b, a wiring trench HM2 is formed.

[0357] As in Embodiment 1, a hard mask (not illustrated) having an opening in a second-level interconnect formation region is formed over the TEOS film 26 c, followed by the formation, over the hard mask, of a resist film (not illustrated) having an opening in a connecting region of the first-level interconnect and the second-level interconnect.

[0358] With the resist film as a mask, the TEOS film 26 c, the low dielectric constant insulating film 26 b, the TEOS films 24 c and 24 a and the SiOC film 24 b are removed to form the contact hole C2. After removal of the resist film, the TEOS films 26 c, 24 c and the low dielectric constant insulating film 26 b are removed with the hard mask as a mask, whereby the wiring trench HM2 is formed. The contact hole C2 may be formed after the formation of the wiring trench HM2.

[0359] The tungsten film CM1 b exposed from the bottom of the contact hole C2 and the tungsten nitride film CM1 a lying thereunder are removed, for example, by dry etching to expose a copper film M1 c.

[0360] Steps on and after the formation of the second-level interconnect M2 and plug (connecting portion) P2 are similar to those of Embodiment 1 so that only their outline will next be described.

[0361] As in Embodiment 1, a barrier film PM2 a is formed over the TEOS film 26 c including the insides of the wiring trench HM2 and contact hole C2. It is deposited to give a thickness of about 5 nm on the side walls of the wiring trench HM2, about 30 nm on the bottom of the wiring trench HM2, about 3 nm on the side walls of the contact hole C2 and about 20 nm on the bottom of the contact hole C2.

[0362] As in Embodiment 1, the barrier film PM2 a is removed from the bottom of the contact hole C2. After deposition of a thin copper film PM2 b as a seed film for electroplating, a copper film PM2 c is formed over the copper film PM2 b by electroplating. In a reducing atmosphere, the substrate 1 is annealed (heat treated), followed by removal of the copper films PM2 c and PM2 b and barrier film PM2 a outside the wiring trench HM2 and contact hole C2 by CMP or etchback, whereby a second-level interconnect M2 and a plug (connecting portion) P2 for connecting the first-level interconnect M1 with the second-level interconnect, each made of the copper films PM2 b, PM2 c and barrier film PM2 a, are formed.

[0363] As in Embodiment 1, a tungsten nitride film CM2 and a tungsten film CM2 b are formed over the second-level interconnect M2 in a similar manner to that employed for the formation of the tungsten nitride film CM1 a and tungsten film CM1 b.

[0364] As illustrated in FIG. 32, a TEOS film 28 a, an SIOC film 28 b and a TEOS film 28 c are then deposited successively, as an insulating film, by CVD over the TEOS film 26 c and tungsten film CM2 b. Over the TEOS film 28 c, a low dielectric constant insulating film 30 b using an aromatic polymer material and a TEOS film (not illustrated) are formed successively as an insulating film.

[0365] In the above-described five-layer insulating film, a wiring trench and a contact hole are formed in a similar manner to that employed for the formation of the wiring trench HM2 and contact hole C2, but illustration of this step is omitted.

[0366] In the above-described manner, the capping conductive films 801, 802 over the interconnects can be formed as a laminate film.

[0367] Also in this Embodiment, since the tungsten film CM1 a, tungsten film CM1 b and barrier film PM2 a between the first-level interconnect M1 and plug P2 are removed, contact resistance therebetween can be reduced. In addition, effects as described in Embodiment 1 such as improvement of electromigration resistance are available.

[0368] (Embodiment 9)

[0369] In Embodiment 1, the diameter of the contact hole was formed substantially equal to the width of the interconnect which lies thereunder. The width of the interconnect under the contact hole may be formed greater than the diameter thereof, or a joint region having a larger diameter than the contact hole may be disposed partially in the interconnect.

[0370] For example, in Embodiment 1, the diameter of the contact hole (such as C2) is almost equal to the width of the interconnect therebelow (for example, the width of M1) as illustrated in FIG. 22. FIG. 33 illustrates the patterns of the first-level interconnect M1, the second-level interconnect M2 and the plug P2 for connecting them. FIG. 34 is a cross-sectional view taken along a line C-C′ of FIG. 33. As illustrated in FIG. 34, a barrier film PM2 a is formed on the side walls or bottom of the contact hole (C2) in which the plug P2 is to be formed and the wiring trench (HM2) in which the second-level interconnect is to be formed. Although not illustrated in the cross-section of FIG. 34, a tungsten film CM1 is formed as a capping conductive film on the surface of the first-level interconnect M1. The barrier film PM2 a and tungsten film CM1 between the plug P2 and interconnect M1 are removed so that contact resistance therebetween can be reduced and effects described in Embodiment 1 such as improvement in electromigration resistance are available.

[0371] As illustrated in FIG. 35, a joint region M901 may be disposed at the end of the first-level interconnect M1. This joint region M901 is formed to have a greater width than the first-level interconnect M1. At the end of the second-level interconnect M2, a joint region M902 is disposed. FIG. 35 illustrates the patterns of the first-level interconnect M1, the second-level interconnect M2 and the plug P2 for connecting them. FIG. 36 is a cross-sectional view taken along a line C-C′ of FIG. 35. As illustrated in FIG. 36, the barrier film PM2 a is formed on the side walls or bottom of the contact hole (C2) in which the plug P2 is to be formed and the wiring trench (HM2) in which the second-level interconnect is to be formed. The tungsten film CM1 is formed as a capping conductive film on the surface of the first-level interconnect M1. On the peripheral surface of the joint region M901, the tungsten film CM1 remains as a capping conductive film.

[0372] Also in this case, the barrier film PM2 a and tungsten film CM1 between the plug P2 and interconnect M1 are removed so that contact resistance therebetween can be reduced and effects described in Embodiment 1 such as improvement in electromigration resistance are available.

[0373] Thus, when wide joint regions M901, M902 are disposed in the interconnect, alignment margin of the plug or interconnect patterns to be formed thereover can be maintained.

[0374] The present invention made by the present inventors was so far described in detail based on Embodiments. It should however be borne in mind that the present invention is not limited to or by them. It can be modified within an extent not departing from the scope of the invention.

[0375] Particularly in Embodiments 1 to 9, the second-level interconnect M2 and connecting portion (plug) P2 were formed using the dual damascene method. They may be formed in respective steps by using the single damascene method. In this case, by removing the capping conductive film on the surface of the first-level interconnect M1 lying under the plug P2 and the barrier film on the bottom of the plug P2, contact resistance can be reduced and electromigration resistance can be improved.

[0376] The insulating film 22 having the barrier insulating film 501 as shown in Embodiment 5 may be applied to Embodiments 2 to 4 and 6 to 9. Even if misalignment occurs, the barrier property against copper diffusion can be maintained on the bottom of the contact hole C2, making it possible to design the width of the first-level interconnect M1 to be equal to the diameter of the contact hole C2, thereby heightening the density and integration degree of interconnects while maintaining the reliability of the interconnects.

[0377] The insulating films 22, 24, 26 shown in Embodiments 2 to 4 may be applied to Embodiments 6 to 9.

[0378] In Embodiment 1, etc., an MISFETQn is given as an example of a semiconductor element, but not only MISFET but also another element such as bipolar transistor may be formed.

[0379] In Embodiment 6, the barrier film PM2 a is disclosed as a barrier material formed as a discontinuous film on the bottom of the contact hole which is a joint portion between the first-level interconnect M1 and plug (connecting portion) P2. The barrier material constituted as a discontinuous film may be formed of not only the above-described barrier film PM2 a, but also the tungsten film CM1 or both of the barrier film PM2 a and tungsten film CM1.

[0380] In Embodiment 1, etc, the planarization of the interlevel insulating film is achieved by using a coating type material, but CMP may be employed for it instead. In Embodiment 1, etc., a difference in etching selectivity ratio of the interlevel insulating films stacked is utilized upon processing of a trench. Alternatively, the trench processing may be terminated before it reaches the bottom of the interlevel insulating film, by controlling the dry etching time or monitoring the etching depth.

[0381] Advantages available by the typical inventions, of the inventions disclosed by the present application, will next be described briefly.

[0382] In a semiconductor device having a wiring portion having on the surface thereof a capping barrier metal film and a connecting portion formed thereover and having, as the periphery thereof, a conductor layer covered with a barrier metal layer, at least either one of the barrier metal layer or capping barrier metal film is removed from a joint between the wiring portion and the connecting portion so that contact resistance therebetween can be reduced. In addition, a generation ratio of voids or disconnection due to electromigration can be reduced. Moreover, the characteristics of the semiconductor device can be improved. 

What is claimed is:
 1. A semiconductor device comprising: a first interlayer insulating film formed over a semiconductor substrate and having a wiring trench; a wiring portion which has a first barrier metal layer formed over the side walls and bottom surface of said wiring trench, a first conductor layer formed over said first barrier metal layer so as to embed said wiring trench, and a capping barrier metal film formed over the surface of said first conductor layer; a second interlayer insulating film formed over said first interlayer insulating film and having a connecting hole; and a connecting portion which has a second barrier metal layer formed over the side walls and bottom surface of said connecting hole, and a second conductor layer formed over said second barrier metal layer so as to embed said connecting hole, wherein at a joint between said connecting portion and said wiring portion, at least either one of said second barrier metal layer or said capping barrier metal film on the bottom surface of said connecting hole is removed.
 2. A semiconductor device comprising a wiring portion and a connecting portion, said wiring portion having a first conductor layer, and a first barrier metal layer formed over the side surfaces and bottom surface of said first conductor layer so as to surround said first conductor layer, and said connecting portion being formed over said wiring portion and having a second conductor layer and a second barrier metal layer formed over the side surfaces of said second conductor layer so as to surround said second conductor layer, wherein at a joint between said connecting portion and said wiring portion, said second barrier metal layer is formed as a discontinuous film on the bottom surface of said second conductor layer.
 3. A semiconductor device comprising a wiring portion and a connecting portion formed in an interlayer insulating film, said wiring portion having a first conductor layer, a first barrier metal layer formed over the side surfaces and bottom surface of said first conductor layer so as to surround said first conductor layer, and a capping barrier metal film formed over the surface of said first conductor layer, said connecting portion having a second conductor layer and a second barrier metal layer formed over at least the side surfaces, among the side surfaces and bottom surface, of said second conductor layer so as to surround said second conductor layer, wherein at a joint between said connecting portion and said wiring portion, either one of said second barrier metal layer or said capping barrier metal film is not formed or is formed as a discontinuous film on the bottom surface of said second conductor layer.
 4. A semiconductor device according to claim 1, wherein at a joint between said wiring portion and said connecting portion, the former is formed to have a larger area than the latter.
 5. A semiconductor device according to claim 1, wherein said capping barrier metal film is not formed only at a joint between said connecting portion and said wiring portion.
 6. A semiconductor device according to claim 1, wherein said second barrier metal layer is removed from the bottom surface of said connecting hole.
 7. A semiconductor device according to claim 1, wherein said second barrier metal layer is not formed over the bottom surface of said second conductor layer.
 8. A semiconductor device comprising a first wiring structure and a second wiring structure, said first wiring structure having a first wiring portion and a first connecting portion formed thereover, said first wiring portion having a first conductor layer, a first barrier metal layer formed over the side surfaces and bottom surface of said first conductor layer so as to surround said first conductor layer, and a first capping barrier metal film formed over the surface of said first conductor layer, said first connecting portion being formed over said first wiring portion and having a second conductor layer, and a second barrier metal layer formed over the side surfaces and the bottom surface of said second conductor layer so as to surround said second conductor layer, said second wiring structure being formed over said first wiring structure and having a second wiring portion and a second connecting portion formed thereover, said second wiring portion having a third conductor layer, a third barrier metal layer formed over the side walls and bottom surface of said third conductor layer so as to surround said third conductor layer, and a second capping barrier metal film formed over the surface of said third conductor layer, and said second connecting portion being formed over said second wiring portion and having a fourth conductor layer and a fourth barrier metal layer formed over the side surfaces and the bottom surface of said fourth conductor layer so as to surround said fourth conductor layer, wherein said first and second barrier metal layers and said first capping barrier metal film are different in structure from said third and fourth barrier metal layers and said second capping barrier metal film, respectively.
 9. A semiconductor device according to claim 8, wherein said second capping barrier metal film is formed thinner than said first capping barrier metal film, or said first capping barrier metal film is formed thinner than said second capping barrier metal film.
 10. A semiconductor device according to claim 8, wherein either one of said fourth barrier metal layer or said second capping barrier metal film is removed from the bottom surface of said fourth conductor layer, and wherein either one of said second barrier metal layer or said first capping barrier metal film is removed from the bottom surface of said second conductor layer.
 11. A semiconductor device according to claim 8, wherein said fourth barrier metal layer and said second capping barrier metal film remain without being removed from the bottom surface of said fourth conductor layer, and wherein either one of said second barrier metal layer or said first capping barrier metal film is removed from the bottom surface of said second conductor layer.
 12. A semiconductor device according to claim 8, wherein said second connecting portion of said second wiring structure has a larger diameter than said first connecting portion of said first wiring structure, or said second wiring portion of said second wiring structure has a larger width than said first wiring portion of said first wiring structure.
 13. A semiconductor device according to claim 8, further comprising a wiring to be connected with said second wiring portion via said second connecting portion, wherein said fourth barrier metal layer and said second capping barrier metal film remain without being removed.
 14. A semiconductor device, comprising: a first insulating film formed over a semiconductor substrate; a second insulating film formed over said first insulating film; a wiring trench formed by selectively removing said first insulating film and said second insulating film; a wiring portion having a first barrier metal layer formed over the side walls and bottom surface of said wiring trench, a first conductor layer formed over said first barrier metal layer so as to embed said wiring trench, and a capping barrier metal film formed over the surface of said first conductor layer; a third insulating film formed over said second insulating film and having a connecting hole; and a connecting portion having a second barrier metal layer formed over at least the side walls, of the side walls and the bottom surface, of said connecting hole, and a second conductor layer formed over said second barrier metal layer so as to embed said connecting hole, wherein said second insulating film has a function as a barrier insulating film.
 15. A semiconductor device according to claim 14, wherein a fourth insulating film having a function as a barrier insulating film is formed over said capping barrier metal film.
 16. A semiconductor device according to claim 14, wherein said second insulating film is a low-dielectric-constant film formed from a material having a lower dielectric constant than that of a silicon nitride film or having a dielectric constant not greater than 5.5.
 17. A semiconductor device according to claim 16, wherein said low dielectric constant film has Si and C, Si and N, Si, C and N, Si, O and N, Si, O and C, or Si, O, C and N; or is a film formed using TMS (trimethoxysilane) and N₂O by CVD.
 18. A semiconductor device according to claim 14, wherein said second insulating film has a function as an etching stopper layer upon formation of said connecting hole.
 19. A semiconductor device according to claim 15, wherein said fourth insulating film has a function as an etching stopper layer upon formation of said connecting hole.
 20. A semiconductor device according to claim 14, wherein said second barrier metal layer is removed from the bottom surface of said connecting hole.
 21. A semiconductor device according to claim 14, wherein said first and third insulating films include a low dielectric constant film formed from a material having a dielectric constant lower than that of a silicon oxide film or having a dielectric constant of 3.7 or less.
 22. A semiconductor device according to claim 21, wherein said low dielectric constant film has Si an C, Si, C and O, Si, O and F, C and H, or Si, O, C and H; or, in addition, is porous.
 23. A semiconductor device according to claim 1, wherein said barrier metal layer is formed from a single layer film of any one of Ta, TaN, TaSiN, W, WN, WSiN, Ti, TiN and TiSiN, or a laminate film obtained by stacking a plurality of any two or greater of Ta, TaN, TaSiN, W, WN, WSiN, Ti, TiN and TiSiN.
 24. A semiconductor device according to claim 1, wherein said capping barrier metal film is formed from a metal layer comprised mainly of W, WN, WSiN and W, a metal layer comprised mainly of CoWP, CoWB or Co, a single layer film of any one of TiN, TiSiN, Ta, TaN and TaSiN, or a laminate film of any two of said metal layers and single layer films.
 25. A semiconductor device according to claim 1, wherein said conductor layer is formed from any one of Cu, a metal layer comprised mainly of Cu, Al, a metal layer comprised mainly of Al, Ag and a metal layer comprised mainly of Ag.
 26. A semiconductor device, comprising: (a) a first conductor layer formed in a first insulating film over a semiconductor substrate; (b) a second insulating film formed over said first insulating film and said first conductor layer; (c) a third insulating film formed over said second insulating film; (d) a wiring trench formed in said third insulating film; (e) a connecting hole formed in said second insulating film and extending from the bottom of said wiring trench to said first conductor layer; (f) a barrier metal layer formed over the side walls and the bottom of said wiring trench and the side walls of said connecting hole; (g) a second conductor layer formed in said wiring trench and connecting hole; and (h) a capping barrier metal film formed between said first conductor layer and said second insulating film, wherein neither said capping barrier metal film nor said barrier metal layer is formed between said first conductor layer and said second conductor layer.
 27. A semiconductor device, comprising: (a) a first conductor layer formed in a first insulating film over a semiconductor substrate; (b) a second insulating film formed over said first insulating film and first conductor layer; (c) a third insulating film formed over said second insulating film; (d) a wiring trench formed in said third insulating film; (e) a connecting hole formed in said second insulating film and extending from the bottom of said wiring trench to said first conductor layer; (f) a barrier metal film formed over the side walls and the bottom of said wiring trench and the side walls and bottom of said connecting hole; (g) a second conductor layer formed in said wiring trench and connecting hole; and (h) a capping barrier metal film formed between said first conductor layer and said second insulating film, wherein said capping barrier metal film is not formed between said first conductor layer and said second conductor layer.
 28. A semiconductor device, comprising: (a) a first conductor layer formed in a first insulating film over a semiconductor substrate; (b) a barrier metal layer formed over said first conductor layer; (c) a second insulating film formed over said first insulating film and barrier metal layer; (d) a third insulating film formed over said second insulating film; (e) a wiring trench formed in said third insulating film; (f) a connecting hole formed in said second insulating film and extending from the bottom of said wiring trench to said barrier metal layer; (g) a barrier metal film formed over the side walls and the bottom of said wiring trench and the side walls of said connecting hole; (h) a second conductor layer formed in said wiring trench and connecting hole, wherein said barrier metal layer is not formed between said first conductor layer and said second conductor layer. 